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2IR.G.KIIELLER I 



THE 

LIFE 

OF 

SIR ISAAC NEWTON 

BY 

DAVID BREWSTER, LL.D. F.R.S. 



Ergo vivida vis anim? pervicit, et extra 

Processit longe flamnwntia moenia mundi ; 

Atque omoe immensum peragravit meote animoque. 

Lttcret. lib. i. 1. 731 




The Birthplace of Ncwtoa. 

NEW-YORK: 

PUBLISHED BY HARPER & BROTHERS, 

NO. 82 C L I F F-S T R E K T. 

1840. 



TO 

THE RIGHT HONOURABLE 

LORD BRAYBROOKE. 



THE kindness with which your lordship intrusted 
to me some very valuable materials for the compo- 
sition of this volume has induced me to embrace the 
present opportunity of publicly acknowledging it. 
But even if this personal obligation had been less 
powerful, those literary attainments and that en- 
lightened benevolence which reflect upon rank its 
highest lustre would have justified me in seeking 
for it the patronage of a name which they have so 
justly honoured* 

DAVID BREWSTER. 

Allerly, June 1st, 1831. 



A/767/7 



PREFACE. 



As this is the only Life of Sir Isaac Newton on 
any considerable scale that has yet appeared, I 
have experienced great difficulty in preparing it for 
the public. The materials collected by preceding 
biographers were extremely scanty ; the particulars 
of his early life, and even the historical details of 
his discoveries, have been less perfectly preserved 
than those of his illustrious predecessors ; and it is 
not creditable to his disciples that they have allowed 
a whole century to elapse without any suitable 
record of the life and labours of a master who 
united every claim to their affection and gratitude. 

In drawing up this volume, I have obtained much 
assistance from the account of Sir Isaac Newton in 
the Biographia Britannica ; from the letters to Ol- 
denburg, arid other papers in Bishop Horsley's 
edition of his works ; from Tumor's Collections for 
the History of the Town and Soke of Grantham ; 
from M. Biot's excellent Life of Newton in the 
Biographic Universelle ; and from Lord King's Life 
and Correspondence of Locke. 

Although these works contain much important 
information respecting the Life of Newton, yet I 
have been so fortunate as to obtain many new ma- 
terials of considerable value. 



10 PREFACE. 

To the kindness of Lord Braybrooke I have been 
indebted for the interesting correspondence of New- 
ton, Mr. Pepys, and Mr. Millington, which is now 
published for the first time, and which throws much 
light upon an event in the life of our author that 
has recently acquired an unexpected and a painful 
importance. These letters, when combined with 
those which passed between Newton and Locke, 
and with a curious extract from the manuscript diary 
of Mr. Abraham Pryme, kindly furnished to me by 
his collateral descendant Professor Pryme of Cam- 
bridge, fill up a blank in his history, and have ena- 
bled me to delineate in its true character that tem- 
porary indisposition which, from the view that has 
been taken of it by foreign philosophers, has been 
the occasion of such deep distress to the friends of 
science and religion. 

To Professor Whewell, of Cambridge, I owe very 
great obligations for much valuable information. 
Professor Rigaud, of Oxford, to whose kindness I 
have on many other occasions been indebted, sup 
plied me with several important facts, and with ex 
tracts from the diary of Hearne in the Bodleian 
Library, and from the original correspondence be- 
tween Newton and Flamstead, which the president 
of Corpus Christi College had for this purpose com- 
mitted to his care ; and Dr. J. C. Gregory, of Edin- 
burgh, the descendant of the illustrious inventor of 
the reflecting telescope, allowed me to use his un- 
published account of an autograph manuscript of 
Sir Isaac Newton, which was found among the pa- 
pers of David Gregory, Savilian Professor of As- 
tronomy at Oxford, and which throws some light on 
the history of the Principia. 



PREFACE. 11 

I have been indebted to many other friends for 
the communication of books and facts, but espe- 
cially to Sir William Hamilton, Bart., whose libe- 
rality in promoting literary inquiry is not limited to 
the circle of his friends. 

D.B. 

Alhrly, June 1st, 1831. 



CONTENTS. 



CHAPTER I. Pag 

The Pre-eminence of Sir Isaac Newton's Reputation The Interest 
attached to the Study of his Life and Writings His Birth and 
Parentage His e^rly Education Is sent to Grantham School 
His early Attachment to Mechanical Pursuits His Windmill 
His Water-clock His Self-moving Cart His Sun-dials His 
Preparation for the University H 

CHAPTER II. 

Newton enters Trinity College, Cambridge Origin of his Propen- 
sity for Mathematics He studies the Geometry of Descartes unas- 
sisted Purchases a Prism Revises Dr. Barrow's Optical Lec- 
tures Dr. Barrow's Opinion respecting Colours Takes his De- 
grees Is appointed a Fellow of Trinity College Succeeds Dr. 
Barrow in the Lucasian Chair of Mathematics 26 

CHAPTER III. 

Newton occupied in grinding Hyperbolical Lenses His first Ex- 
periments with the Prism made in 1666 He discovers the Com- 
position of White Light, and the different Refrangibility of the 
Rays which compose it Abandons his Attempts to improve Re- 
fracting Telescopes, and resolves to attempt the Construction of 
Reflecting ones He quits Cambridge on account of the Plague 
Constructs two Reflecting Telescopes in 1668, the first ever exe- 
cutedOne of them examined by the Royal Society, and shown 
to the King He constructs a Telescope with Glass Specula Re- 
eent History of the Reflecting Telescope Mr. Airy's Glass Specula 
Hadley's Reflecting Telascopes Short's Berschel's -Ram- 
age*s Lord Oxmantown's 30 

CHAPTER IV. 

He delivers a Course of Optical Lectures at Cambridge Is elected 
Fellow of the Royal Society He communicates to them his Dis- 
coveries on the different Refrangibility and Nature of Light- 
Popular Account of them They involve him in various Contro- 
versiesHis Dispute with Pardies Linus Lucas Dr. Hooke 

. and Mr. Huygens The Influence of these Disputes on the mind 
of Newton 47 

CHAPTER V. 
Mistake of Newton in supposing that the Improvement of Befraot- 

B 



14 CONTENTS. 

Pag 

ing Telescopes was hopeless Mr. Hall invents the Achromatic 
Telescope Principles of the Achromatic Telescope explained It 
is reinvented by Dollond, and improved by future Artists Dr. 
Blair's Aplanatic Telescope Mistakes in Newton's Analysis of 
the Spectrum Modern Discoveries respecting the Structure of 
the Spectrum 63 

CHAPTER VI. 

Colours of thin Plates first studied by Boyle and Hooke Newton 
determines the Law of their Production His Theory of Fits of 
easy Reflection and Transmission Colours of thick Plates 75 

CHAPTER VII. 

Newton's Theory of the Colours of Natural Bodies explained Ob- 
jections to it stated New Classification of Colours Outline of a 
new Theory proposed 89 

CHAPTER VIII. 

Newton's Discoveries respecting the Inflection or Diffraction of 
Light Previous Discoveries of Grimaldi and Dr. Hooke Labours 
of succeeding Philosophers Law of Interference of Dr. Young 
Fresnel's Discoveries New Theory of Inflection on the Hypothe- 
sis of the Materiality of Light 99 

CHAPTER IX. 

Miscellaneous Optical Researches of Newton His Experiments on 
Refraction His Conjecture respecting the Inflammability of the 
Diamond His Law of Double Refraction His Observations on 
the Polarization of Light Newton's Theory of Light His " Op- 
tics" 106 

CHAPTER X. 

Astronomical Discoveries of Newton Necessity of combined Exer 
tion to the completion of great Discoveries Sketch of the History 
of Astronomy prexrfous to the time of Newton Copernicus, 1473 
-1543 TychoBrahe, 1546-1601 Kepler, 1571-1631 Galileo, 1564 
-1642 110 

CHAPTER XI. 

The first Idea of Gravity occurs to Newton in 1666 His first Specu- 
lations upon it Interrupted by his Optical Experiments He 
resumes the Subject in consequence of a Discussion with Doctor 
Hooke He discovers t'je true Law of Gravity and the Cause of 
the Planetary Motions Dr. Halley urges him to publish his Prin- 
cipia His Principles of Natural Philosophy Proceedings of the 
Royal Society on this Subject The Principia appears in 1687 
General Account of it, and of the Discoveries it contains They 
meet with great Opposition, owing to the Prevalence of the Carte- 
sian System Account of the Reception and Progress of the New- 
tonian Philosophy in Foreign Countries Account of its Progress 
and Establishment in England 140 



CONTENTS. 15 

CHAPTER XIL Paga 

Doctrine of Infinite Quantities Labours of Pappus Kepler Cava- 
leri Roberval Fermat Wallis Newton discovers the Bino- 
mial Theorem and the Doctrine of Fluxions in 16C6 His Manu- 
script Work containing this Doctrine communicated to his Friends 
His Treatise on Fluxions His Mathematical Tracts His Uni- 
versal Arithmetic His Methodus Differentials His Geornetria 
Analytica His Solution of the Problems proposed by Bernouilli 
and Leibnitz Account of the celebrated Dispute respecting the 
Invention of Fluxions Commercium Epistolicurn Report of the 
Royal Society General View of the Controversy 168 

CHAPTER Xin. 

James IT. attacks the Privileges of the University of Cambridge 
Newton chosen one of the Dtlegates to resist this Encroachment 
He is elected a Member of the Convention Parliament Burning 
of his Manuscript His supposed Derangement of Mind View 
taken of this by foreign Philosophers His Correspondence with 
Mr. Pepys and Mr. Locke at the time of his Illness Mr. Milling- 
ton's Letter to Mr. Pepys on the subject of Newton's Illness 
Refutation of the Statement that he laboured under Mental De- 
rangement 200 

CHAPTER XIV. 

No Mark of National Gratitude conferred upon Newton Friendship 
between him and Charles Montague, afterward Earl of Halifax 
Mr. Montague appointed Chancellor of the Exchequer in 1604 
He resolves upon a Recoinage Nominates Mr. Newton Warden 
of the Mint in 1695 Mr. Newton appointed Master of the Mint in 
1699 Notice of the Earl of Halifax Mr. Newton elected Asso- 
ciate of the Academy of Sciences in 1699 Member for Cambridge 
in 1701 and President cf the Royal Society in 1703 Queen Anne 
confers upon him the Honour of Knighthood in 1705 Second 
Edition of the Principia, edited by Cotes His Conduct respectvjg 
Mr. Ditton's Method of finding the Longitude 223 

CHAPTER XV. 

Respect in which Newton was held at the Court of George I. The 
Princess of Wales delighted with his Conversation Leibnitz en- 
deavours to prejudice the Princess against Sir Isaac and Locke ' 
Controversy occasioned by his Conduct The Princess obtains a 
Manuscript Abstract of his System of Chronology The Abbe 
Conti is, at her request, allowed to take a Copy of it on the prom- 
ise of Secrecy He prints it surreptitiously in French, accompa- 
nied with a Refutation by M. Freret Sir Isaac's Defence of his 
System Father Souciet attacks it, and is answered by Dr. Halley 
Sir Isaac's larger Work on Chronology published afler his 
DeathOpinions respecting it Sir Isaac's Paper on the Form of 
the most ancient Year 234 

CHAPTER XVI. 

Theological Studies of Sir Isaac Their Importance to Christianity 
-Motives to which they have been ascribed Opinions of Biot 



16 CONTENTS. 

Faff 

and La Place considered His Theological Researches begun be- 
fore his supposed Mental Illness The Date of these Works fixed 
Letters to Locke Account of his Observations on Prophecy 
His Lexicon Propheticum His Four Letters to Dr. Bentley Ori 
gin of Newton's Theological Studies Analogy between the Book 
of Nature and that of Revelation 242 

CHAPTER XVH. 

The Minor Discoveries and Inventions of Newton His Researches 
on Heat On Fire and Flame On Elective Attraction On the 
Structure of Bodies His supposed Attachment to Alchymy His 
Hypothesis respecting Ether as the Cause of Light and Gravity 
On the Excitation of Electricity in Glass His Reflecting Sex- 
tant invented before 1700 His Reflecting Microscope His Pris- 
matic Reflector as a Substitute for the small Speculum of Reflect- 
ing Telescopes His Method of varying the Magnifying Power of 
Newtonian Telescopes His Experiments on Impressions on the 
Retina 265 

CHAPTER XVIII. 

His Acquaintance with Dr. Pemberton Who edits the Third Edi- 
tion of the Principia His first Attack of ill Health His Recovery 
He is taken ill in consequence of attending the Royal Society 
His Death on the 20th March, 1727 His Body lies in state His 
Funeral He is buried in Westminster Abbey His Monument de- 
scribed His Epitaph A Medal struck in honour of him Roubil- 
iac's full-length Statue of him erected in Cambridge Division 
of his Property His Successors 284 

CHAPTER XIX. 

Permanence of Newton's Reputation Character of his Genius 
His Method of Investigation similar to that used by Galileo 
Error in ascribing his Discoveries to the Use of the Methods 
recommended by Lord Bacon The Pretensions of the Baconian 
Philosophy examined Sir Isaac Newton's Social Character His 
great Modesty The Simplicity of his Character His Religious 
and Moral Character His Hospitality and Mode of Life His 
Generosity and Charity His Absence His Personal Appear- 
anceStatues and Pictures of him Memorials and Recollections 
of him 292 



APPENDIX, No. I. Observations on the Family of Sir Isaac New- 
ton 307 

APPENDIX, No. n. Letter from Sir Isaac Newton to Francis Aston, 
Esq., a young Friend who was on the eve of setting out on his 
Travels 318 

APPENDIX, No. HI. " A Remarkable and Curious Conversation be- 
tween Sir Isaac Newton and Mr. Conduit." 320 



LIFE 

off 
SIR ISAAC NEWTON. 



CHAPTER I. 

The Pre-eminence of Sir Isaac Newton's Reputation The Interest 
attached to the Study of his Life and Writings His Birth and 
Parentage His early Education Is sent to Grantham School His 
early Attachment to Mechanical Pursuits His WindmillHis 
Waterclock His Selfmoving Cart His Sundials His Preparation 
for the University. 

THE name of Sir Isaac Newton has by general 
consent been placed at the head of those great men 
who have been the ornaments of their species. 
However imposing be the attributes with which 
time has invested the sages and the heroes of anti- 
quity, the brightness of their fame has been eclipsed, 
by the splendour of his reputation ; and neither the 
partiality of rival nations, nor the vanity of a presump- 
tuous age, has ventured to dispute the ascendency 
of his genius. The philosopher,* indeed, to whom 
posterity will probably assign the place next to New- 
ton, has characterized the Principia as pre-eminent 
above all the productions of human intellect, and 
has thus divested of extravagance the contemporary 
encomium upon its author, 

Nee fas est propius mortal! attingere Divos. 

HALLET. 
So near the gods man cannot nearer go. 

I . 

* The Marquis La Place. See Systtme du Monde, p. 336. 
B2 



18 SIR ISAAC NEWTON 

The biography of an individual so highly renowned 
cannot fail to excite a general interest. Though 
his course may have lain in the vale of private life, 
and may have been unmarked with those dramatic 
events which throw a lustre even round perishable 
names, yet the inquiring spirit will explore the his- 
tory of a mind so richly endowed, will study its 
intellectual and moral phases, and will seek the 
shelter of its authority on those great questions 
which reason has abandoned to faith and hope. 

If the conduct and opinions of men of ordinary 
talent are recorded for our instruction, how inter- 
esting must it be to follow the most exalted genius 
through the incidents of common life ; to mark the 
steps by which he attained his lofty pre-eminence ; 
to see how he performs the functions of the social 
and the domestic compact; how he exercises his 
lofty powers of invention and discovery; how he 
comports himself in the arena of intellectual strife ; 
and in what sentiments, and with what aspirations 
he quits the world which he has adorned. 

In almost all these bearings, the life and writings 
of Sir Isaac Newton abound with the richest counsel. 
Here the philosopher will learn the art by which 
alone he can acquire an immortal name. The mor- 
alist will trace the lineaments of a character ad- 
justed to all the symmetry of which our imperfect 
nature is susceptible; and the Christian will con- 
template with delight the high-priest of science 
quitting the study of the material universe, the 
scene of his intellectual triumphs, to investigate 
with humility and patience the mysteries of his faith. 

Sir Isaac Newton was born at Woolsthorpe, a 
hamlet in the parish of Colsterworth, in Lincoln- 
shire, about six miles south of Grantham, on the 
25th December, O. S., 1642, exactly one year after 
Galileo died, and was baptized at Colsterworth on 
the 1st January, 1643-3. His father, Mr. Isaac New- 



BIRTH. 19 

ton, died at the early age of thirty-six, a little more 
than a year after the death of his father Robert 
Newton, and only a few months after his marriage 
to Harriet Ayscough, daughter of James Ayscough 
of Market Overton in Rutlandshire. This lady was 
accordingly left in a state of pregnancy, and appears 
to have given a premature birth to her only and 
posthumous child. The helpless infant thus ushered 
into the world WPS of such an extremely diminutive 
size,* and seemed of so perishable a frame, that 
two women who were sent to Lady Pakenham's at 
North Witham, to bring some medicine to strengthen 
him, did not expect to find him alive on their return. 
Providence, however, had otherwise decreed; and 
that frail tenement which seemed scarcely able to 
imprison its immortal mind was destined to enjoy 
a vigorous maturity, and to survive even the average 
term of human existence. The estate of Wools- 
thorpe, in the manor-house of which this remarka- 
ble birth took place, had been more than a hundred 
years in the possession of the family, who came 
originally from Newton in Lancashire, but who had, 
previous to the purchase of Woolsthorpe, settled at 
Westby, in the county of Lincoln. The manor- 
house, of which we have given an engraving, is 
situated in a beautiful little valley, remarkable for 
its copious wells of pure spring water, on the west 
side of the river Witham, which has its origin in the 
neighbourhood, and commands an agreeable pros- 
pect to the east towards Colsterworth. The manor 
of Woolsthorpe was worth only 30Z. per annum; 
but Mrs. Newton possessed another small estate at 
Sewstern,f which raised the annual value of their 
property to about 80Z. ; and it is probable that the 
cultivation of the little farm on which she resided 

* Sir Isaac Newton told Mr. Conduit, that he had often heard his 
mother say that when he was born he was so little that they might 
have put him into a quart mug. 

t In Leicestershire, and about three miles south-east of Woolsthorpe. 



20 SIR ISAAC NEWTON. 

somewhat enlarged the limited income upon which 
she had to support herself, and educate her child. 

For three years Mrs. Newton continued to watch 
over her tender charge with parental anxiety ; but 
in consequence of her marriage to the Reverend 
Barnabas Smith, rector of North Witham, about a 
mile south of Woolsthorpe, she left him under the 
care of her own mother. At the usual age he was 
sent to two day-schools at Skillington and Stoke, 
where he acquired the education which such semi- 
naries afforded; but when he reached his twelfth 
year he went to the public school at Grantham, 
taught by Mr. Stokes, and was boarded at the house 
of Mr. Clark, an apothecary in that town. Accord- 
ing to information which Sir Isaac himself gave to 
Mr. Conduit, he seems to have been very inattentive 
to his studies, and very low in the school. The 
boy, however, who was above him, having one day 
given him a severe kick upon his stomach, from 
which he suffered great pain, Isaac laboured inces- 
santly till he got above him in the school, and from 
that time he continued to rise till he was the head 
boy. From the habits of application which this 
incident had led him to form, the peculiar character 
of his mind was speedily displayed. During the 
hours of play, when the other boys were occupied 
with their amusements, his mind was engrossed with 
mechanical contrivances, either in imitation of some- 
thing which he had seen, or in execution of some 
original conception of his own. For this purpose 
he provided himself with little saws, hatchets, ham- 
mers, and all sorts .of tools, which he acquired the 
art -of using with singular dexterity. The principal 
pieces of mechanism which he thus constructed 
were a windmill, a waterclock, and a carriage put in 
motion by the person who sat in it. When a wind- 
mill was erecting near Grantham on the road to 
Gunnerby, Isaac frequently attended the operations 
of the workmen, and acquired such a thorough 



MECHANICAL PURSUITS. 21 

knowledge of the machinery that he completed a 
working model of it, which excited universal admi- 
ration. This model was frequently placed on the top 
of the house in which he lodged at Grantham, and 
was put in motion by the action of the wind upon 
its sails. Not content with this exact imitation of 
the original machine, he conceived the idea of driv- 
ing it by animal power, and for this purpose he en- 
closed in it a mouse which he called the miller, and 
which, by acting upon a sort of treadwheel, gave 
motion to the machine. According to some ac- 
counts, the mouse was made to advance by pulling 
a string attached to its tail, while others allege that 
the power of the little agent was called forth by its 
unavailing attempts to reach a portion of corn placed 
above the wheel. 

His waterclock was formed out of a box which 
he had solicited from Mrs. Clark's brother. It was 
about four feet high, and of a proportional breadth, 
somewhat like a common houseclock. The index 
of the dialplate was turned by a piece of wood, which 
either fell or rose by the action of dropping water. 
As it stood in his own bedroom he supplied it every 
morning with the requisite quantity of water, and it 
was used as a clock by Mr. Clark's family, and re- 
mained in the house long after its inventor had 
quitted Grantham.* His mechanical carriage was a 
vehicle with four wheels, which was put in motion 
with a handle wrought by the person who sat in it, 
but, like Merlin's chair, it seems to have been used 
only on the smooth surface of a floor, and not fitted 
to overcome the inequalities of a road. Although 

< 

* "I remember once," says Dr. Stukely, "when I was deputy to 
Dr. Halley, secretary at the Royal Society, Sir Isaac talked of these 
kind of instruments. That he observed the chief inconvenience in 
them was, that the hole through which the water is transmitted being 
necessarily very small, was subject to be furred up by impurities in the 
water, as those made with sand will wear bigger, which at length causes 
an inequality in time." Stukely 's Letter to Dr. Mead. Tumor's CoZ- 
lections, p. 177. 



22 SIR ISAAC NEWTON. 



Newton was at this time " a sober, silent, thinking 
lad," who scarcely ever joined in the ordinary games 
of his schoolfellows, yet he took great pleasure in 
providing them with amusements of a scientific 
character. He introduced into the school the flying 
of paper kites ; and he is said to have been at great 
pains in determining their best forms and propor- 
tions, and in ascertaining the position and number 
of the points by which the string should be attached. 
He made also paper lanterns, by the light of which 
he went to school in the winter mornings, and he 
frequently attached these lanterns to the tails of 
his kites in a dark night, so as to inspire the country 
people with the belief that they were comets. 

In the house where he lodged there were some 
female inmates in whose company he appears to have 
taken much pleasure. One of these, a Miss Storey, 
sister to Dr. Storey, a physician at Buckminster, 
near Colsterworth, was two or three years younger 
than Newton, and to great personal attractions she 
seems to have added more than the usual allotment 
of female talent. The society of this young lady 
and her companions was always preferred to that 
of his own schoolfellows, and it was one of his most 
agreeable occupations to construct for them little 
tables and cupboards, and other utensils for holding 
their dolls and their trinkets. He had lived nearly 
six years in the same house with Miss Storey, and 
there is reason to believe that their youthful friend- 
ship gradually rose to a higher passion; but the 
smallness of her portion and the inadequacy of his 
own fortune appear to have prevented the consum- 
mation of their happiness. Miss Storey was after- 
ward twice married, and under the name of Mrs. 
Vincent, Dr. Stukely visited her at Grantham in 1727, 
at the age of eighty-two, and obtained from her 
many particulars respecting the early history of our 
author. Newton's esteem for her continued un- 
abated during his life. He regularly visited her when 



SUNDIALS. 23 

he went to Lincolnshire, and never failed to relieve 
her from little pecuniary difficulties which seem to 
have beset her family. 

Among the early passions of Newton we must 
recount his love of drawing ; and even of writing 
verses. His own room was furnished with pictures 
drawn, coloured, and framed by himself, sometimes 
from copies, but often from life.* Among these 
were portraits of Dr. Donne, Mr. Stokes, the master 
of Grantham school, and King Charles I. under 
whose picture were the following verses. 

A secret art my soul requires to try, 
If prayers can give me what the wars deny. 
Three crowns distinguished here, in order do 
Present their objects to my knowing view. 
Earth's crown, thus at my feet I can disdain, 
Which heavy is, and at the best but vain. 
But now a crown of thorns I gladly greet, 
Sharp is this crown, but not so sharp as sweety 
The crown of glory that I yonder see 
Is full of bliss and of eternity. 

These verses were repeated to Dr. Stukely by Mrs. 
Vincent, who believed them to be written by Sir 
Isaac, a circumstance which is the more probable, 
as he himself assured Mr. Conduit, with some ex- 
pression of pleasure, tHat he " excelled in making 
verses," although he had been heard to express a 
contempt for poetical composition. 

But while the mind of our young philosopher was 
principally occupied with the pursuits which we have 
now detailed, it was not inattentive to the move- 
ments of the celestial bodies, on which he was des- 
tined to throw such a brilliant light. The imperfec- 
tions of his watei clock had probably directed his 
thoughts to the more accurate measure of time which 
the motion of the sun afforded. In the yard of the 

* Mr. Clark informed Dr. Stukely that the walls of the room in which 
Sir Isaac lodged were covered with charcoal drawings of birds, beasts, 
men, ships, and mathematical figures, ail of which were very well de- 
signed. 



24 SIR ISAAC NEWTON. 

house where he lived, he traced the varying move- 
ments of that luminary upon the walls and roofs of the 
buildings, and by means of fixed pins he had marked 
out the hourly and half-hourly subdivisions. One 
of these dials, which went by the name of Isaac's 
<foz/,and was often referred to by the country people 
for the hour of the day, appears to have been drawn 
solely from t"Lo observations of several years ; but 
we are not informed whether all the dials *which he 
drew on the wall of his house at Woolsthorpe, and 
which existed after his death, were of the same 
description, or were projected from his knowledge 
of the doctrine of the sphere. 
> Upon the death of the Reverend Mr. Smith in the 
year 1656, his widow left the rectory of North 
Witham, and took up her residence at Woolsthorpe 
along with her three children, Mary, Benjamin, and 
Hannah* Smith. Newton had now attained the 
fifteenth year of his age, and had made great pro- 
gress in his studies ; and as he was thought capable 
of being useful in the management of the farm and 
country business at Woolsthorpe, his mother, chiefly 
from a motive of economy, recalled him from the 
school at Grantham. In order to accustom him to 
the art of selling and buying, two of the most im- 
portant branches of rural labour, he was frequently 
sent on Saturday to Grantham market to dispose 
of grain and other articles of farm produce, and to 
purchase such necessaries as the family required. 
As he had yet acquired no experience, an old trust- 
worthy servant generally accompanied him on these 
errands. The inn which they patronised was the 
Saracen's Head at West Gate ; but no sooner had 
they put tip their horses than our young philosopher 
deserted his commercial concerns, and betook him- 
self to his former lodging in the apothecary's garret, 
where a number of Mr. Clark's old books afforded 
him abundance of entertainment till his aged guar- 
dian had executed the family commissions, and a& 



PREPARATION FOR THE UNIVERSITY. 2 

nounced to him the necessity of returning. At other 
times he deserted his duties at an earlier stage, and 
intrenched himself under a hedge by the way-side, 
where he continued his studies till the servant re- 
turned from Grantham. The more immediate affairs 
of the farm were not more prosperous under his 
management than would have been his marketings 
at Grantham. The perusal of a book, the execu- 
tion of a model, or the superintendence of a water- 
wheel of his own construction, whirling the glitter- 
ing spray from some neighbouring stream, absorbed 
all his thoughts when the sheep were going astray, 
and the cattle were devouring or treading down the 
corn. 

Mrs. Smith was soon convinced from experience 
that her son was not destined to cultivate the soil, 
and as his passion for study, and his dislike for every 
other occupation increased with his years, s?ie wisely 
resolved to give him all the advantages which edu- 
cation could confer^ He was accordingly sent back 
to Grantham school, where he continued for some 
months in busy preparation for his academical stu- 
dies. His uncle, the Reverend W. Ayscough, who 
was rector of Burton Goggles, about three miles 
east of Woolsthorpe, and who had himself studied 
at Trinity College, recommended to his nephew to 
enter that society, and it was accordingly determined 
that he should proceed to Cambridge at the ap- 
proaching term.* 

* " One of his uncles," says M. Biot, " having one day found him 
under a hedge with a book in his hand and entirely absorbed in medita- 
tion, took it from him, and found that he was occupied in the solution of a 
mathematical problem. Struck with finding so serious and so active 
a disposition at so early an age, he urged his mother no longer to thwart 
iHm, and to send him back to Grantham to continue his studies." I 
hsve omitted this anecdote in the text, as I cannot find it in Tumor's 
Collections, from which M. Biot derived his details of Newton's infancy, 
Ifcr in any other work. 

c 



26 SIR ISAAC NEWf ON. 



CHAPTER II. 

fffwton enters Trinity College, CambridgeOrigin of his Propensity 
for Mathematics He studies the Geometry ofDetcartes unassisted- 
Purchases a Prism Revises Dr. Harrow's Optical Lectures Dr 
Barrow's Opinion respecting Colours. Takes his Degrees Is ap- 
pointed a Fellow of Trinity College Succeeds Dr. Barrow in the 
Lucasian Chair of Mathematics. 

To a young mind thirsting for knowledge, and 
ambitious of the distinction which it brings, the 
transitibn from a village school to a university like 
that of Cambridge, from the absolute solitude of 
thought to the society of men imbued with all the 
literature and science of the age, must be one of 
eventful interest. To Newton it was a source of 
peculiar excitement. The history of science affords 
many examples where the young aspirant had been 
early initiated into her mysteries, and had even ex- 
ercised his powers of invention and discovery before 
he was admitted within the walls of a college ; but he 
who was to give philosophy her laws did not exhibit 
such early talent ; no friendly counsel regulated his 
youthful studies, and no work of scientific eminence 
seems to have guided him in his course. In yield- 
ing to the impulse of his mechanical genius, his 
mind obeyed the laws of its own natural expansion, 
and, following the line of least resistance, it was 
thus drawn aside from the strongholds with which 
it was destined to grapple. 

When Newton, therefore, arrived at Trinity Col- 
lege, he brought with him a more slender portion of 
science than falls to the lot of ordinary scholars ; 
but this state of his acquirements was perhaps not 
unfavourable to the development of his powers. 
Unexhausted by premature growth, and invigorated 
by healthful repose, his mind was the better fitted to 



TRINITY COLLEGE. 27 

make those vigorous and rapid shoots which soon 
covered with foliage and with fruit the genial soil 
to which it had been transferred. 
^Cambridge was consequently the real birthplace 
of Newton's genius. Her teachers fostered his ear- 
liest studies ; her institutions sustained his mightiest 
efforts ; and within her precincts were all his dis- 
coveries made and perfected. When he was called 
to higher official functions, his disciples kept up the 
pre-eminence of their master's philosophy, and their 
successors have maintained this seat of learning in, 
the fulness of its glory, and rendered it the most 
distinguished among the universities of Europe. 

It was on the 5th of June, 1660, in the 18th year 
of his age, that Newton was admitted into Trinity 
College, Cambridge, during the same year that Dr. 
Barrow was elected professor of Greek in the uni- 
versity. His attention was first turned to the study 
of mathematics by a desire to inquire into the truth 
of judicial astrology ; and he is said to have dis- 
covered the folly of that study by erecting a figure 
with the aid of one or two of the problems of 
Euclid. The propositions contained in this ancient 
system of geometry he regarded as self-evident 
truths ; and without any preliminary study he made 
himself master of Descartes's Geometry by his 
genius and patient application. This neglect of the 
elementary truths of geometry he afterward regarded 
as a mistake in his mathematical studies, and he ex- 
pressed to Dr. Pemberton his regret that " he had ap- 
plied himself to the works of Descartes, and other alge- 
oraic writers, before he had considered the elements 
of Euclid with that attention which so excellent a 
writer deserved.* Dr. Wallis's Arithmetic of Infinites, 
^aunderson's Logic, and the Optics of Kepler were 
among the books which he had studied with care. On 
these works he wrote comments during their perusal $ 

* Pemberton's View of Sir Isaac Newton 1 s Philosophy. Pref. _, 



28 SIR ISAAC NEWTON. 

and so great was his progress, that he is reported to 
have found himself more deeply versed in some 
branches of knowledge than the tutor who directed 
his studies. 

Neither history nor tradition has handed down to 
us any particular account of his progress during the 
first three years that he spent at Cambridge. It 
appears from a statement of his expenses, that in 
1664 he purchased a prism, for the purpose, as has 
been said, of examining rtescartes's theory of co- 
lours ; and it is stated by Mr. Conduit, that he soon 
established his own views on the subject, and de- 
tected the errors in those of the French philosopher. 
This, however, does not seem to have been the case. 
Had he discovered the composition of light in 1664 
or 1665, it is not likely that he would have withheld 
it, not only from the Royal Society, but from his 
own friends at Cambridge till the year 1671. His 
friend and tutor, Dr. Barrow, was made Lucasian 
Professor of Mathematics in 1663, and the optical 
lectures which he afterward delivered were published 
in 1669. In the preface of this work he acknow- 
ledges his obligations to his colleague, Mr. Isaac 
Newton,* for having revised the MSS., and corrected 
several oversights, and made some important sug- 
gestions. In the twelfth lecture there are some ob- 
servations on the nature and origin of colours, 
which Newton could not have permitted his friend 
to publish had he been then in possession of their 
true theory. According to Dr. Barrow, White is 
that which discharges a copious light equally clear 
in eveiy direction; Black is that which does not 
emit light at all, or which does it very sparingly. 
Red is that which emits a light more clear than 
usual, but interrupted by shady interstices. Blue is 
that which discharges a rarified light, as in bodies 
which consist of white and black particles arranged 

* Peregregiae vir indolls ac insignia peritiee. Epist ad. Lect 



APPOINTED PROFESSOR ~OF MATHEMATICS. 29 

alternately. Green is nearly allied to blue. Yellow 
is a mixture of much white and a little red; and 
Purple consists of a great deal of blue mixed with 
a small portion of red. . The blue colour of the sea 
arises from the whiteness of the salt which it con- 
tains, mixed with tjie blackness of the pure water 
in which the salt is dissolved ; and the blueness of 
the shadows of bodies, seen at the same time by 
candle and daylight, arises from the whiteness of 
the paper mixed with the faint light or blackness of 
the twilight. These opinions savour so little of 
genuine philosophy that they must have attracted 
the observation of Newton, and had he discovered 
at that time that white was a mixture of all the 
colours, and black a privation of them all, he could 
not have permitted the absurd speculations of his 
! master to pass uncorrected. 

That Newton had not distinguished himself by 
! any positive discovery so early as 1664 or 1665, may 
! be inferred also from the circumstances which at- 
! tended the competition for the law fellowship of 
j Trinity College. The candidates for this appoint- 
| ment were himself and Mr. Robert Uvedale ; and 
j Dr. Barrow, then Master of Trinity, having found 
j them perfectly equal in their attainments, con- 
! ferred the fellowship on Mr. Uvedale as the senior 
I candidate. 

In the books of the university, Newton is recorded 
j as having been admitted sub-sizer in 1661. He 
! became a scholar in 1664. In 1665 he took his de- 
gree of Bachelor of Arts, and in 1666, in conse- 
quence of the breaking out of the plague, he retired 
to Woolsthorpe. In 1667 he was made Junior Fel- 
low. In 1668 he took his degree of Master of Arts, 
and in the same year he was appointed to a Senior 
Fellowship. In 1669, when Dr. Barrow had re- 
solved to devote his attention to theology, he re- 
signed the Lucasian Professorship of Mathematics 
in favour of Newton, who may now be considered 
C2 



30 SIR ISAAC NEWTON. 

as having entered upon that brilliant career of dis- 
covery the history of which will form the subject of 
some of the following chapters. 



CHAPTER III. 

Newton occupied in grinding Hyperbolical Lenses His first Experi- 
ments with the Prism made in 1666 He discovers the Composition of 
White Light, and the different Refrangibility of the Rays which com- 
pose it Abandons his Attempts to improve Refracting Telescopes and 
resolves to attempt the Construction of Reflecting ones He quits Cam- 
bridge on account of the Plague Constructs two Reflecting Telescopes 
in 1668, the first, ever executed One of them examined by the Royal So- 
ciety, and shown to the King He constructs a Telescope with Glass 
Specula Recent History of the Reflecting Telescope Mr. Airy's 
Glass Specula Hadleifs Reflecting Telescopes Short's HerscheCs 
Ramage's Lord Oxmantowrts. 

THE appointment of Newton to the Lucasian 
chair at Cambridge seems to have been coeval with 
his grandest discoveries. The first of these of 
which the date is well authenticated is that of the 
different refrangibility of the rays of light, which he 
established in 1666. The germ of the doctrine of 
universal gravitation seems to have presented itself 
to him in the same year, or at least in 1667 and u in 
the year 1666 or before"* he was in possession of 
his method of fluxions, and he had brought it to such 
a state in the beginning of 1669, that he permitted 
Dr. Barrow to communicate it to Mr. Collins on the 
20th of June in that year. 

Although we have already mentioned, on the au- 
thority of a written memorandum of Newton him 
self, that he purchased a prism at Cambridge in 1664, 
yet he does not appear to have made any use of it, 
as he informs us that it was in 1666 that he "pro- 

* See Newton's Letter to the Abbe Conti, dated February 26, 1715-lft 
hi the Additamenta Comm. Epistotici. 



REFRACTING TELESCOPE. 31 

cured a triangular glass prism to try therewith the 
celebrated phenomena of colours."* During that 
year he had applied himself to the grinding of " op- 
tic glasses, of other figures than spherical," and 
having, no doubt, experienced the impracticability 
of executing such lenses, the idea of examining the 
phenomena of colour was one of those sagacious 
and fortunate impulses which more than once led 
him to discovery. Descartes in his Dioptrice, pub- 
lished in 1629, and more recently James Gregory in 
his Optica Promota published in 1663, had shown 
that parallel and diverging rays could be reflected or 
refracted, with mathematical accuracy, to a point or 
focus, by giving the surface a parabolic, an elliptical, 
or a hyperbolic form, or some other form not spher- 
ical. Descartes had even invented and described 
machines by which lenses of these shapes could be 
ground and polished, and the perfection of the re- 
fracting telescope was supposed to depend on the 
degree of accuracy with which they could be exe- 
cuted. 

In attempting to grind glasses that were not spher- 
ical, Newton seems to have conjectured that the de- 
fects of lenses, and consequently of refracting tele- 
scopes, might arise from some other cause than the 
imperfect convergency of rays to a single point, and 
this conjecture was happily realized in those fine 
discoveries of which we shall now endeavour to 
give some account. 

! When Newton began this inquiry, philosophers of 
the highest genius were directing all the energies of 
their mind to the subject of light, and to the im- 
provement of the refracting telescope. James 
Gregory of Aberdeen had invented his reflecting 
telescope. Descartes had explained the theory and 
exerted himself in perfecting the construction of the 
common refracting telescope, and Huygens had not 

Newtoni Opera, torn, iv. p. 205, Letter to Oldenburg. 



32 SIR ISAAC NEWTON. 

only executed the magnificent instruments by which 
he discovered the ring and the satellites of Saturn, 
but had begun those splendid researches respecting 
the nature of light, and the phenomena of double 
refraction, which have led his successors to such 
brilliant discoveries. Newton, therefore, arose when 
the science of light was ready for some great ac- 
cession, and at the precise time when he was re- 
quired to propagate the impulse which it had received 
from his illustrious predecessors. 

The ignorance which then prevailed respecting 
the nature and origin of colours is sufficiently ap- 
parent from the account we have already given of 
Dr. Barrow's speculations on this subject. It was 
always supposed that light of every colour was 
equally refracted or bent out of its direction when 
it passed through any lens or prism, or other refract- 
ing medium ; and though the exhibition of colours 
by the prism had been often made previous to the 
time of Newton, yet no philosopher seems to have 
attempted to analyze the phenomena. 

When he had procured his triangular glass prism, 
a section of which is shown at ABC, (fig. 1,) he 

Fig. 1. 




made a hole H in one of his window-shutters, SHT 
and having darkened his chamber, he let in a con- 
venient quantity of the sun's light RR, which, pass- 



EXPERIMENTS ON COLOURS. 33 

ing through the prism ABC, was so refracted as to 
exhibit all the different colours on the wall at MN, 
forming an image about five times as long as it was 
broad. "It was at first," says our author, "a very 
pleasing divertisement to view the vivid and intense 
colours produced thereby," but this pleasure was 
immediately succeeded by surprise at various circum- 
stances which he had not expected. According to 
the received laws of refraction, he expected the 
image MN to be circular, like the white image at W, 
which the sunbeam RR had formed on the wall 
previous to the interposition of the prism ; but when 
he found it to be no less than five times larger than 
its breadth, it "excited in him a more than ordinary 
curiosity to examine from whence it might proceed. 
He could scarcely think that the various thickness of 
the glass, or the termination with shadow or dark- 
ness, could have any influence on light to produce such 
an effect: yet he thought it not amiss first to examine 
those circumstances, and so find what would happen 
by transmitting light through parts of the glass of 
divers thicknesses, or through holes in the window 
of divers bignesses, or by setting the prism without 
(on the other side of ST), so that the light might 
pass through it and be refracted before it was termi- 
nated by the hole ; but he found none of these cir- 
cumstances material. The fashion of the colours 
was in all those cases the same." 

Newton next suspected that some unevenness in 
the glass, or other accidental irregularity, might 
cause the dilatation of the colours. In order to try 
this, he took another prism BCB', and placed it in 
such a manner that the light RRW passing through 
them both might be refracted contrary ways, and 
thus returned by BCB' into that course RRW, from 
which the prism ABC had diverted it, for by this 
means he thought the regular effects of the prism 
ABC would be destroyed by the prism BCB, and the 
irregular ones more augmented by the multiplicity 



34 SIR ISAAC NEWTON. 

of refractions. The result was, that the light which 
was diffused by the first prism ABC into an oblong 
form, was reduced by the second prism BCB' into a 
circular one W, with as much regularity as when it 
did not pass through them at all; so that whatever 
was the cause of the length of the image MN, it did 
not arise from any irregularity in the prism. 

Our author next proceeded to examine more critic- 
ally what might be effected by the difference of the 
incidence of "the rays proceeding from different parts 
of the sun's disk ; but by taking accurate measures 
of the lines and angles, he found that the angle of 
the emergent rays should be 31 minutes equal to the 
sun's diameter, whereas the real angle subtended by 
MN at the hole H was 2 49'. But as this computa- 
tion was founded on the hypothesis, that the sine of 
the angle of incidence was proportional to the sine 
of the angle of refraction, which from his own ex- 
perience he could not imagine to be so erroneous as 
to make that angle but 31', which was in reality 2 
49', yet " his curiosity caused him again to take up 
his prism" ABC, and having turned it round in both 
directions, so as to make the rays RR fall both with 
greater and with less obliquity upon the face AC, he 
found that the colours on the wall did not sensibly 
change their place ; and hence he obtained a decided 
proof that they could not be occasioned by a differ- 
ence in the incidence of the light radiating from dif- 
ferent parts of the sun's disk. 

Newton then began to suspect that the rays, after 
passing through the prism, might move in curve lines, 
and, in proportion to the different degrees of curva- 
ture, might tend to different parts of the wall; and 
this suspicion was strengthened by the recollection 
that he had often seen a tennis-ball struck with an 
oblique racket describe such a curve line. In this 
case a circular and a progressive motion is commu- 
nicated to the ball by the stroke, and in consequence 
of this, the direction of its motion was curvilineal, 



sot 1 



EXPERIMENTS ON COLOURS. 35 

so that if the rays of light were globular bodies, 
they might acquire a circulating motion by their ob- 
ilique passage out of one medium into another, and 
thus move like the tennis-ball in a curve line. Not- 
withstanding, however, "this plausible ground of 
suspicion," he could discover no such curvature in 
their direction, and, what was enough for his pur- 

Eose, he observed that the difference between the 
?ngth MN of the image, and the diameter of the 
! hole H, was proportional to their distance HM, 
which could not have happened had the rays moved 
in curvilineal paths. 

These different hypotheses, or suspicions, as New- 
jton calls them, being thus gradually removed, he 
was at length led to an experiment which deter- 
mined beyond a doubt the true cause of the elonga- 
tion of the coloured image. Having taken a board 
with a small hole in it, he placed it behind the face 
BC of the prism, and close to it, so that he could 
transmit through the hole any one of the colours in 
MN, and keep back all the rest. When the hole, 
for example, was near C, no other light but the red 
fell upon the wall at N. He then placed behind N 
another board with a hole in it, and behind this 
board he placed another prism, so as to receive the 
red light at N, which passed through this hole in the 
second board. He then turned round the first prism 
ABC so as to make all the colours pass in succession 
through these two holes, and he marked their places 
on the wall. From the variation of these places, 
he saw that the red rays at N were less refracted by 
the second prism than the orange rays, the orange 
less than the yellow, and so on, the violet being more 
refracted than all the rest. 

Hence he drew the grand conclusion, that light 
leas not homogeneous, but consisted of rays, some of 
which were more refrangible than others. 

As soon as this important truth was established, 
Sir Isaac saw that a lens which refracts light exactly 



36 SIR ISAAC NEWTON. 

like a prism must also refract the differently colourec 
rays with different degrees of force, bringing the 
violet rays to a focus nearer the glass than the rec 
rays. This is shown in Jig. 2, where LL is a con 
vex lens, and S, L, SL rays of the sun falling upon i 

Fig. 2. 

M 




M 



in parallel directions. The violet rays existing in 
the white light SL being more refrangible than the 
rest, will be more refracted or bent, and will meet al 
V, foiming there a violet image of the sun. In like 
manner the yellow rays will form an image of the 
sun at Y, and so on, the red rays, which are the least 
refrangible, being brought to a focus at R, and there 
forming a red image of the sun. 

Hence, if we suppose LL to be the object-glass of 
a telescope directed to the sun, and MM an eye-glass 
through which the eye at E sees magnified the image 
or picture of the sun formed by LL, it cannot see| 
distinctly all the different images between R and V. 
If it is adjusted so as to see distinctly the yellow 
ima^e at Y, as it is in the figure, it will not see dis- 
tinctly either the red or violet images, nor indeed any 
of them but the yellow one. There will conse- 
quently be a distinct yellow image, with indistinct 
images of all the other colours, producing great cone- 
fusion and indistinctness of vision. As soon as Sir 
Isaac perceived this result of his discovery, he aban- 
doned his attempts to improve the refracting tele- 



IMPERFECTIONS OF TELESCOPES. 37 

scope, and took into consideration the principle of re- 
jection; and as he found that rays of all colours 
were reflected regularl) , so that the angle of reflec- 
tion was equal to the angle of incidence, he con- 
pluded that, upon this principle, optical instruments 
Plight be brought to any degree of perfection imaginable, 
[provided a reflecting substance could be found which 
3ould polish as finely as glass, and reflect as much 
light as glass transmits, and provided a method of 
:ommunicating to it a parabolic figure could be ob- 
tained. These difficulties, however, appeared to him 
very great, and he even thought them insuperable 
when he considered that, as any irregularity in a re- 
lecting surface makes the rays deviate five or six 
times more from their true path than similar irregu- 
.arities in a refracting surface, a much greater de- 
gree of nicety would be required in figuring reflect- 
ing specula than refracting lenses. 

Such was the progress of Newton's optical dis- 
coveries, when he was forced to quit Cambridge in 
1666 by the plague which then desolated England, 
and more than two years elapsed before he pro- 
ceeded any farther. In 1668 he resumed the inquiry, 
and having thought of a delicate method of polish- 
ng, proper ( for metals, by which, as he conceived, 
'the figure would be corrected to the last," he began 
;o put this method to the test of experiment. At 
,his time he was acquainted with the proposal of 
Mr. James Gregory, contained in his Optica Promota, 
o construct a reflecting telescope with two concave 
specula, the largest of which had a hole in the 
middle of the larger speculum, to transmit the light 
o an eye-glass;* but he conceived that it would be 

* M. Biot, in his Life of Newton, has stated that Newton was pre- 
ceded in the invention of the reflecting telescope by Gregory, but proba- 
Ay without knowing it. It is quite certain, however, that Newton was 
icquainted with Gregory's invention, as appears from the following 
avowal of it. " When I first applied myself to try the effects of reflec- 
tion, Mr. Gregory's Optica Promota (printed in the year 1663) having 
fallen into my hands, where there is an instrument described with a hole 



38 SIR ISAAC NEWTON. 

an improvement on this instrument to place the eye* 
glass at the side of the tube, and to reflect the rays 
to it by an oval plane speculum. One of these 
instruments he actually executed with his own 
hands ; and he gave an account of it in a letter to a 
friend, dated February 23d, 1668-9, a letter which is 
also remarkable for containing the first allusion to 
his discoveries respecting colours. Previous to this 
he was in correspondence on the subject with Mr. 
Ent, afterward Sir George Ent, one of the original 
council of the Royal Society, an eminent medical 
writer of his day, and President of the College of- 
Physicians. In a letter to Mr. Ent he had promised 
an account of his telescope to their mutual friend, 
and the letter to which we now allude contained tne 
fulfilment of that promise. The telescope was six 
inches long. It bore an aperture in the large specu- 
lum something more than an inch, and as the eye- 
glass was a plano-convex lens, whose focal length 
was one-sixth or one-seventh of an inch, it magni- 
fied about forty times, which, as Newton remarks, 
was more than any six-foot tube (meaning refracting 
telescopes) could do with distinctness. On account 
of the badness of the materials, however, and the 
want of a good polish, it represented objects less 
distinct than a six-feet tube, though h3 still thought 
it would be equal to a three or four feet tube di- 
rected to common objects. He had seen through it 
Jupiter distinctly with his four satellites, and also 
the horns or moon-like phases of Venus, though this 
last phenomenon required some niceness in adjusting 
the instrument. 

Although Newton considered this little instru- 



in the midst of fne object-glass, to transmit the light to an eye-glass 
placed behind it, I had thence an occasion of considering that sort of con- 
struction, and found their disadvantages so great, that I saw it necessary 
before I attempted any thing in the practice to alter the design of them 
and place the eye-glass at the side of the tube rather than at the middle. 



REFLECTING TELESCOPE. 89, 

it as in itself contemptible, yet he regarded it as 
an u epitome of what might be done ;" and he ex- 
pressed his conviction that a six-feet telescope might 
be made after this method, which would perform as 
well as a sixty or a hundred feet telescope made in 
the common way; and that if a common refracting 
;elescope could be made of the "purest glass exqui- 
sitely polished, with the best figure that any geo- 
metrician (Descartes, &c.) hath or can design," it 
would scarcely perform better than a common tele- 
scope. This, he adds, may seem a paradoxical as- 
iertion, yet he continues, " it is the necessary con- 
sequence of some experiments which I have made 
concerning the nature of light." 

The telescope now described possesses a very pe- 
culiar interest, as being the first reflecting one which 
was ever executed and directed to the heavens, 
ames Gregory, indeed, had attempted, in 1664 or 
665, to construct his instrument. He employed 
Messrs. Rives and Cox, who were celebrated glass- 
Tinders of that time, to execute a concave speculum 
f six feet radius, and likewise a small one; but as 
hey had failed in polishing the large one, and as Mr. 
~ regory was on the eve of going abroad, he troubled 
limself no farther about the experiment, and the 
ube of the telescope was never made. Some time 
afterward, indeed, he " made some trials both with a 
ittle concave and convex speculum," but, "pos^- 
iessed with the fancy of the defective figure, hi 
would not be at the pains to fix every thing in its due 
Listance." 

Such were the earliest attempts to construct the 
eflecting telescope, that noble instrument which 
las since effected such splendid discoveries in as- 
ronomy. Looking back from the present advanced 
itate of practical science, how great is the contrast 
>etween the loose specula of Gregory and the fine 
Gregorian telescopes of Hadley, Short, and Veitch, 
-between the humble six-inch tube of Newton and 
the gigantic instruments of Herschel and Ramage. 



40 SIR ISAAC NEWTON. 

The success of this first experiment inspired New- 
ton with fresh zeal, and though his mind was now 
occupied with his optical discoveries, with the ele- 
ments of his method of fluxions, and with the ex- 
panding germ of his theory of universal gravitation, 
yet with all the ardour of youth he applied himself 
to the laborious operation of executing another re- 
flecting telescope with his own hands. This instru- 
ment, which was better than the first, though it lay 
by him several years, excited some interest at Cam- 
bridge ; and Sir Isaac himself informs us, that one 
of the fellows of Trinity College had completed a 
telescope of the same kind, which he considered as 
somewhat superior to his own. The existence of 
these telescopes having become known to the Royal 
Society, Newton was requested to send his instru- 
ment for examination to that learned body. He ac- 
cordingly transmitted it to Mr. Oldenburg in Decem- 
ber, 1671, and from this epoch his name began to 
acquire that celebrity by which it has been so pecu- 
liarly distinguished. 

On the llth of January, 1672, it was announced 
to the Royal Society that his reflecting telescope 
had been shown to the king, and had been examined 
"by the president, Sir Robert Moray, Sir Paul Neale, 
Sir Christopher Wren, and Mr, Hook. These gen- 
tlemen entertained so high an opinion of it, that, in 
qjder to secure the honour of the contrivance to its 
author, they advised the inventor to send a drawing 
and description of it to Mr. Huygens at Paris. Mr. 
Oldenburg accordingly drew up a description of it 
in Latin, which, after being corrected by Mr. New- 
ton, was transmitted to that eminent philosopher. 
This telescope, of which the annexed is an accurate 
drawing, is carefully preserved in the library of the 
Royal Society of London, with the following in- 
scription : 

" Invented by Sir Isaac Newton and made with his 
own hands 1671." 






REFLECTING TELESCOPES. 



41 




42 SIR ISAAC NEWTOX. 

It does not appear that Newton executed any other 
reflecting telescopes than the two we have mentioned. 
He informs us that he repolished and greatly im- 
proved a fourteen-feet object-glass, executed by a 
London artist, and having proposed in 1678 to sub- 
stitute glass reflectors in place of metallic specula, 
he tried to make a reflecting telescope on this 
principle four feet long, and with a magnifying power 
of 150. The glass was wrought by a London artist, 
and though it seemed well finished, yet, when it was 
quicksilvered on its convex side, it exhibited all over 
the glass innumerable inequalities, which gave an 
indistinctness to every object. He expresses, how- 
ever, his conviction that nothing but good work- 
manship is wanting to perfect these telescopes, and 
he recommends their consideration " to the curious 
in figuring glasses." 

For a period of fifty years this recommendation 
excited no notice. At last Mr. James Short of 
Edinburgh, an artist of consummate skill, executed 
about the year 1730 no fewer than six reflecting 
telescopes with glass specula, three of fifteen inches, 
and three of nine inches in focal length. He found 
it extremely troublesome to give them a true figure 
with parallel surfaces ; and several of them when 
finished turned out useless, in consequence of the 
veins which then appeared in the glass. Although 
these instruments performed remarkably well, yet 
the light was fainter than he expected, and from this 
cause, combined with the difficulty of finishing them, 
he afterward devoted his labours solely to those 
with metallic specula. 

At a later period, in 1822, Mr. G. B. Airy of 
Trinity College, and one of the distinguished suc- 
cessors of Newton in the Lucasian chair, resumed 
the consideration of glass specula, and demonstrated 
that the aberration both of figure and of colour 
might be corrected in these instruments. Upon this 
ingenious principle Mr. Airy executed more than 



REFLECTING TELESCOPES. 43 

one telescope, but though the result of the experi- 
ment was such as to excite hopes of ultimate suc- 
cess, yet the construction of such instruments is 
still a desideratum in practical science. 

Such were the attempts which Sir Isaac Newton 
made to construct reflecting telescopes ; but notwith- 
standing the success of his labours, neither the phi- 
losopher nor the practical optician seems to have 
had courage to pursue them. A London artist, in- 
deed, undertook to imitate these instruments ; but 
Sir Isaac informs us, that " he fell much short of 
what he had attained, as he afterward understood 
by discoursing with the under workmen he had em- 
ployed." After a long period of fifty years, John 
Hadley, Esq. of Essex, a Fellow of the Royal So- 
ciety, began in 1719 or 1720 to execute a reflecting 
telescope. His scientific knowledge and his manual 
dexterity fitted him admirably for such a task, and, 
probably after many failures, he constructed two 
large telescopes about five feet three inches long, 
one of which, with a speculum six inches in diameter, 
was presented to the Royal Society in 1723. The 
celebrated Dr. Bradley and the Rev. Mr. Pound 
compared it with the great Huygenian refractor 123 
feet long. It bore as high a magnifying power as 
the Huygenian telescope : it showed objects equally 
distinct, though not altogether so clear and bright, 
and it exhibited every celestial object that had been 
discovered by Huygens, the five satellites of Sat- 
urn, the shadow of Jupiter's satellites on his disk, 
the black list in Saturn's ring, and the edge of his 
shadow cast on the ring. Encouraged and instructed 
by Mr. Hadley, Dr. Bradley began the construction 
of reflecting telescopes, and succeeded so well that 
he wo Aid have completed one of them, had he not 
been obliged to change his residence. Some time 
afterward he and the Honourable Samuel Molyneux 
undertook the task together at Kew, and attempted 
to execute specula about twenty-six inches in focal 



44 SIR ISAAC NEWTON. 

length ; but notwithstanding Dr. Bradley's former 
experience, and Mr. Hadley's frequent instructions, 
it was a long time before they succeeded. The first 
good instrument which they finished was in May, 
1724. It was twenty-six inches in focal length ; but 
they afterward completed a very large one of eight 
feet, the largest that had ever been made. The first 
of these instruments was afterward elegantly fitted 
up by Mr. Molyneux, and presented to Ins majesty 
John V. King of Portugal. 

The great object of these two able astronomers 
was to reduce the method of making specula to 
such a degree of certainty that they could be manu- 
factured for public sale. Mr. Hauksbee had indeed 
made a good one about three and a half feet long, 
and had proceeded to the execution of two others, 
one of six feet, and another of twelve feet in focal 
length ; but Mr. Scarlet and Mr. Hearne, having re- 
ceived all the information which Mr. Molyneux had 
acquired, constructed them for public sale ; and the 
reflecting telescope has ever since been an article of 
trade with every regular optician. 

As Sir Isaac Newton was at this time President 
of the Royal Society, he had the high satisfaction 
of seeing his own invention become an instrument 
of public use, and of great advantage to science, 
and he no doubt felt the full influence of this triumph 
of his skill. Still, however, the reflecting telescope 
had not achieved any new discovery in the heavens. 
The latest accession to astronomy had been made 
Dy the ordinary refractors of Huygens, labouring 
under all the imperfections of coloured light ; and 
this long pause in astronomical discovery seemed 
to indicate that man had carried to its farthest limits 
his power of penetrating into the depths of the uni- 
verse. This, however, was only one of those sta- 
tionary positions from which human genius takes a 
new and a loftier elevation. While the English op- 
ticians were thus practising the recent art of grinding 



DR. HEUSCHEL'S TELESCOPES. 45 

specula, Mr. James Short of Edinburgh was devot- 
ing to the subject all the energies of his youthful 
mind. In 1732, and in the 22d year of his age, he 
began his labours, and he carried to such high per- 
fection the art of grinding and polishing specula, and 
of giving them the true parabolic figure, that, with. 
a telescope fifteen inches in focal length, he read in 
the Philosophical Transactions at the distance of 
500 feet, and frequently saw the five satellites of 
Saturn together, a power which was beyond the 
reach even of Hadley's six-feet instrument. The 
celebrated Maclaurin compared the telescopes of 
Short with those made b}^ the best London artists, 
and so great was their superiority, that his small 
telescopes were invariably superior to larger ones 
from London. In 1742, after he had settled as an 
optician in the metropolis, he executed for Lord 
Thomas Spencer a reflecting telescope, twelve feet 
in focal length, for 630/. ; in 1752 he completed one for 
the King of Spain, at the expense of 1200/. ; and a 
short time before his death, which took place in 
1768, he finished the specula of the large telescope 
which was mounted equatorially for the observatory 
of Edinburgh by his brother Thomas Short, who was 
offered twelve hundred guineas for it by the King of 
Denmark. 

Although the superiority of these instruments, 
which were all of the Gregorian form, demonstrated 
the value of the reflecting telescope, yet no skilful 
hand had yet directed it to the heavens ; and it was 
reserved for Dr. Herschel to employ it as an instru- 
ment of discovery, to exhibit to the eye of man new 
worlds and new systems, and to bring within the 
grasp of his reason those remote regions of space 
to which his imagination even had scarcely ventured 
to extend its power. So early as 1774 he completed 
a five-feet Newtonian reflector, and he afterward 
executed no fewer than two hundred 7 feet, one hun- 
dred and fifty 10 feet, and eighty 20 feet specula. In 



"46 SIR ISAAC NEWTON. 

1781 he began a reflector thirty feet long, and having 
a speculum thirty-six inches in diameter ; and under 
the munificent patronage of George III. he com- 
pleted, in 1789, his gigantic instrument forty feet 
long, with a speculum forty-nine and a half inches 
in diameter. The genius and perseverance which 
created instruments of such traiiscendant magnitude 
were not likely to terminate with their construction. 
In the examination of the starry heavens, the ulti- 
mate object of his labours. Dr. Herschel exhibited 
the same exalted qualifications, and in a few years 
he rose from the level of humble life to the enjoy- 
ment of a name more glorious than that of the sages 
and warriors of ancient times, and as immortal as 
the objects with which it will be for ever associated. 
Nor was it in the ardour of the spring of life that 
these triumphs of reason were achieved. Dr. Her- 
schel had reached the middle of his course before 
his career of discovery began, and it was in the au- 
tumn and winter of his days that he reaped the full 
harvest of his glory. The discovery of a new planet 
at the verge of the solar system was the first trophy 
of his skill, and new double and multiple stars, and 
new nebulae, and groups of celestial bodies were 
added in thousands to the system of the universe. 
The spring-tide of knowledge which was thus let in 
upon the human mind continued for a while to spread 
its waves over Europe ; but when it sank to its ebb in 
England, there was no other bark left upon the strand 
but that of the Deucalion of Science, whose home 
had been so long upon its waters. 

During the life of Dr. Herschel, and during the 
reign, and within the dominions of his royal patron, 
four new planets were added to the solar system, 
but they were detected by telescopes of ordinary 
power ; and we venture to state, that since the reign 
of George III no attempt has been made to keep 
up the continuity of Dr. Herschel's discoveries. 

Mr. Herschel, his distinguished son, has indeed 



ELECTED INTO THE ROYAL SOCIETY. 47 

c **pleted more than one telescope of considerable 
size ; Mr. Ramage, of Aberdeen, has executed re- 
flectors rivalling almost those of Slough ; and Lord 
Oxmantown, an Irish nobleman of high promise, is 
now engaged on an instrument of great size. But 
what avail the enthusiasm and the efforts of indi- 
vidual minds in the intellectual rivalry of nations ? 
When the proud science of England pines in obscu- 
rity, blighted by the absence of the royal favour, and 
of the nation's sympathy; when its chivalry fall 
unwept and unhonoured ; how can it sustain the 
conflict against the honoured and marshalled genius 
of foreign lands ? 



CHAPTER IV. 

He delivers a Course of. Optical Lectures at Cambridge Is elected Fellow 
of the Royal Society He communicates to them his Discoveries on 
the different Refrangibility and Nature of LightPopular Account 
of them They involve him in various Controversies His Dispute 
with Pardies Linus Lucas Dr. Hooke and Mr. HuygensTh* 
Influence of these Disputes on the Mind of Newton. 

ALTHOUGH Newton delivered a course of lectures 
on optics in the University of Cambridge in the 
years 1669, 1670, and 1671, containing his principal 
discoveries relative to the different refrangibility of 
light, yet it is a singular circumstance, that these 
discoveries should not have become public through 
the conversation or correspondence of his pupils. 
The Royal Society had acquired no knowledge of 
them till the beginning of 1672, and his reputation 
; in that body was founded chiefly on his reflecting 
' telescope. On the 23d December, 1671, the cele- 
brated Dr. Seth Ward, Lord Bishop of Sarum, who 
was the author of several able works on astronomy, 
and had filled the astronomical chair at Oxford, 
proposed Mr. Newton as a Fellow of the Royal 



48 SIR ISAAC NEWTON. 

Society. The satisfaction which he derived from this 
circumstance appears to have been considerable ; 
and in a letter to Mr. Oldenburg, of the 6th January, 
he says, " I am very sensible of the honour done 
me by the Bishop of Sarum in proposing me a can- 
didate ; and which, I hope, will be further conferred 
upon me by my election into the Society ; and if 
so, I shall endeavour to testify my gratitude, by 
communicating what my poor and solitary endeav- 
ours can effect towards the promoting your philo- 
sophical designs." His election accordingly took 
place on the llth January, the same day on which 
the Society agreed to transmit a description of his 
telescope to Mr. Huygens at Paris. The notice of 
his election, and the thanks of the Society for the 
communication of his telescope, were conveyed in 
the same letter, with an assurance that the Society 
" would take care that all right should be done him 
in the matter of this invention." In his next letter 
to Oldenburg, written on the 18th January, 1671-2, 
he announces his optical discoveries in the following 
remarkable manner : " 1 desire that in your next 
letter you would inform me for what time the So- 
ciety continue their weekly meetings ; because if 
they continue them for any time, I am purposing 
them, to be considered of and examined, an account 
of a philosophical discovery which induced me to the 
making of the said telescope ; and I doubt not but 
will prove much more grateful than the communica- 
tion of that instrument ; being in my judgment the 
oddest, if not the most considerable detection which 
hath hitherto been made in the operations of nature." 
This " considerable detection" was the discovery 
of the different refrangibility of the rays of light 
which we ^ave already explained, and which led 
to the construction of his reflecting telescope. It 
was communicated to the Royal Society in a letter 
to Mr. Oldenburg, dated February 6th, and excited 
great interest among its members. The "solemn 



COMMUNICATES HIS DISCOVERIES. 49 

thanks" of the meeting were ordered to be trans- 
mitted to its author for his "very ingenious dis- 
course." A desire was expressed to have it imme- 
diately printed, both for the purpose of having it 
well considered by philosophers, and for " securing 
the considerable notices thereof to the author against 
the arrogations of others ;" and Dr. Seth Ward, 
Bishop of Salisbury, Mr. Boyle, and Dr. Hooke 
were desired to peruse and consider it, and to bring 
in a report upon it to the Society. 

The kindness of this distinguished body, and the 
anxiety which they had already evinced for his 
reputation, excited on the part of Newton a corres- 
ponding feeling, and he gladly accepted of their pro- 
posal to publish his discourse in the monthly num- 
bers in which the Transactions were then given to 
the world. " It was an esteem," says he,* " of the 
Royal Society for most candid and able judges in 
philosophical matters, encouraged me to present 
them with that discourse of light and colours, which 
since they have so favourably accepted of, I do ear- 
nestly desire you to return them my cordial thanks. 
I before thought it a great favour to be made a 
member of that honourable body; but I am now 
more sensible of .the advantages; for believe me, 
sir, I do not only esteem it a duty to concur with 
you in the promotion of real knowledge ; but a great 
privilege, that, instead of exposing discourses to a 
prejudiced and common multitude, (by which means 
many truths have been baffled and lost), I may with 
freedom apply myself to so jpdicious and impartial 
an assembly. A s to the printing of that letter, I am 
satisfied in theii judgment, or else I should have 
thought it too straight and narrow for public view. 
I designed it only to those that know how to im- 
prove upon hints of things ; and, therefore, to spare 
tediousness, omitted many such remarks and ex* 

* Letter to Oldenburg, February 10, 1671. 
E 



50 SIR ISAAC NEWTON. 

periments as might be collected by considering the 
assigned laws of refractions ; some of which I be- 
lieve, with the generality of men, would yet be 
almost as taking as any I described. But yet, since 
the Royal Society have thought it fit to appear pub- 
licly, 1 leave it to their pleasure : and perhaps to 
supply the aforesaid defects, I may send you some 
more of the experiments to second it (if it be so 
thought fit), in the ensuing Transactions." 

Folio wing the order which Newton himself adopted, 
we have, in the preceding chapter, given an account 
of the leading doctrine of the different refrangibility 
of light, and of the attempts to improve the reflect- 
ing telescope which that discovery suggested. We 
shall now, therefore, endeavour to make the reader 
acquainted with the other discoveries respecting 
colours which he at this time communicated to the 
Royal Society. 

Having determined, by experiments 
already described, that a beam of 
white light, as emitted from the sun, 
consisted of seven different colours, 
which possess different degrees of 
refrangibility, he measured the re- 
lative extent of the coloured sp^es, 
and found them to have the propor- 
tions shown in Jig. 4, which rep- 
resents the prismatic spectrum, and 
, u hich is nothing more than an elon- 
gated image of the sun produced by 
the rays being separated in different 
degrees from their original direction, 
the red being refracted least, and the 
violet most powerfully. 

If we consider light as consisting 
of minute particles of matter, we may 
form some notion of its decomposi- 
tion by the prism from the following 
popular illustration. If we take steel 



Fig. 4. 




Orange 



Yellow 



Green 



Blue 



Indigo 



Violet 



DECOMPOSITION OF lIGHT. 51 

filings of seven different degrees of fineness and 
mix them together, there are two ways in which we 
i may conceive the mass to be decomposed, or, what 
I is the same thing, all the seven different kinds of 
| filings separated from each other. By means of 
[seven sieves of different degrees of fineness, and so 
Imade that the finest will just transmit the finest 
powder and detain all the rest, while the next in 
fineness transmits the two finest powders and detains 
all the rest, and so on, it is obvious that all the pow- 
ders may be completely separated from each other. 
If we again mix all the steel filings, and laying them 
upon a table, hold high above them a flat bar magnet, 
so that none of the filings are attracted, then if we 
bring the magnet nearer and nearer, we shall come 
to a point where the finest filings are drawn up to it. 
These being removed, and the magnet brought 
nearer still, the next finest powders will be attracted, 
and so on till we have thus drawn out of the mass 
all the powders in a separate state. We may con- 
ceive the bar magnet to be inclined to the surface 
of the steel filings, and so moved over the mass, 
that at the end nearest to them the heaviest or 
coarsest will be attracted, and all the remotest and 
the finest or ligfflrer filings, while the rest are at- 
tracted to intermediate points, so that the seven 
different filings are not only separated, but are found 
adhering in separate patches to the surface of the 
flat magnet. The first of these methods, with the 
sieves, may represent the process of decomposing 
light, by which certain rays of white light are ab- 
sorbed, or stifled, or stopped in passing through 
bodies, while certain other rays are transmitted. 
The second method may represent the process of 
decomposing light by refraction, or by the attraction 
of certain rays farther from their original direction 
than other rays, and the different patches of filings 
upon the flat magnet may represent the spaces on 
the spectrum. 



52 SIR ISAAC NEWTON. 

When a beam of white light is decomposed into 
the seven different colours of the spectrum, any 
particular colour, when once separated from the 
rest, is not susceptible of any change, or farther 
decomposition, whether it is refracted through prisms 
or reflected from mirrors. It may become fainter 
or brighter, but Newton never could, by any process, 
liter its colour or its refrangibility. 

Among the various bodies which act upon light, 
it is conceivable that there might have been some 
which acted least upon the violet rays and most 
upon the red rays. Newton, however, found that 
this never took place ; but that the same degree of 
refrangibility always belonged to the same colour, 
and the same colour to the same degree of refran- 
gibility. 

Having thus determined that the seven different 
colours of the spectrum were original or simple, he 
was led to the conclusion that whiteness or white 
light is a compound of all the seven colours of the 
spectrum, in the proportions in which they are rep- 
resented in Jig. 4. In order to prove this, or what 
is called the recomposition of white light out of the 
seven colours, he employed three different methods. 

When the beam RR was sepltated into its ele- 




mentary colours by the prism ABC, he received the 



RECOMPOSIT10N Of LIGHT. 53 

Colours on another prism BOB', held either close to 
the first or a little behind it, and by the opposite re- 
fraction of this prism they were all refracted back 
into a beam of white light BW, which formed a 
white circular image on the wall at W, similar to 
what took place before any of the prisms were 
placed in its way. 

The other method of recomposing white light 
consisted in making the spectrum fall upon a lens at 
some distance from it. When a sheet of white 
paper was held behind the lens, and removed to a 
proper distance, the colours were all refracted into 
a circular spot, and so blended as to reproduce light 
so perfectly white as not to differ sensibly from the 
direct light of the sun. 

The last method of recomposing white light was 
one more suited^to vulgar apprehension. It con- 
sisted in attempting to compound a white by mix- 
ing the coloured powders used by painters. He 
was aware that such colours, from their very nature, 
could not compose a pure white ; but even this im- 
perfection in the experiment he removed by an in- 
genious device. Me accordingly mixed one part of 
red lead, four parts of blue bice, and a proper propor- 
tion of orpiment and verdigris. This mixture was 
dun, like wood newly cut, or like the human skin. 
He now took one-third of the mixture and rubbed 
it thickly on the floor of his room, where the sun 
shone upon it through the opened casement, and be- 
side it, in the shadow, he laid a piece of white paper 
of the same size. " Then going from them to the 
distance of twelve or eighteen feet, so that he could 
not discern the unevenness of the surface of the 
powder nor the little shadows let fall from the gritty 
particles thereof; the powder appeared intensely 
white, so as to transcend even the paper itself in 
whiteness." By adjusting the relative illumination 
of the powders and the paper, he was able to 
make them both appear of the very same degree 01 
E2 



64 SIR ISAAC NEWTON. 

whiteness. "For," says he, "when I was trying 
this, a friend coming to visit me, I stopped him at 
the door, and before I told him what the colours 
were, or what I was doing, I asked him which of the 
two whites were the best, and wherein they differed? 
And after he had at that distance viewed them well, he 
answered, that they were both good whites, and that 
he could not say which was best, nor wherein their 
colours differed." Hence Newton inferred that 
perfect whiteness may be compounded of different 
colours. 

As all the various shades of colour which appear 
in the material world can be imitated by intercept- 
ing certain rays in the spectrum, and uniting all the 
rest, and as bodies always appear of the same colour 
as the light in which they are placed, he concluded, 
that the colours of natural bodies are not qualities 
inherent in the bodies themselves, but arise from the 
disposition of the particles of each body to stop or 
absorb certain rays, and thus to reflect more copiously 
the rays which are not thus absorbed. 

No sooner were these discoveries given to the 
world than they were opposed with a degree of viru- 
lence and ignorance which have seldom been com- 
bined in scientific controversy. Unfortunately for 
Newton, the Royal Society contained few individuals 
of pre-eminent talent capable of appreciating the 
truth of his discoveries, and of protecting him against 
the shafts of his envious and ignorant assailants. 
This eminent body, while they held his labours in 
the highest esteem, were still of opinion that his 
discoveries were fair subjects of discussion, and 
their secretary accordingly communicated to him all 
the papers which were written in opposition to his 
views. The first of these was by a Jesuit named 
Ignatius Pardies, Professor of Mathematics at Cler- 
mont, who pretended that the elongation of the sun's 
image arose from the inequal incidence of the dif- 
ferent rays on the first face of the prism, although 



vv 

le 
bi 



CONTROVERSY WITH LINUS. 65 

Newton Tiad demonstrated in his own discourse that 
this was not the case. In April, 1672, Newton trans- 
mitted to Oldenburg a decisive reply to the animad- 
versions of Pardies ; but, unwilling to be vanquished, 
this disciple of Descartes took up a fresh position, 
and maintained that the elongation of the spectrum 
/might be explained by the diffusion of light on the 
hypothesis of Grimaldi, or by the diffusion of undu- 
lations on the hypothesis of Hook. Newton again 
replied to these feeble reasonings ; but he contented 
himself with reiterating 1 his original experiments, 
and confirming them by more popular arguments, 
and the vanquished Jesuit wisely quitted the field. 

Another combatant soon sprung up in the person 
of one Francis Linus, a pt^sician in Liege,* who, 
on the 6th October, 1674, addressed a letter to a 
friend in London, containing animadversions on 
Newton's doctrine of colours. He boldly affirms, 
that in a perfectly clear sky the image of the sun 
made by a prism is never elongated, and that the 
spectrum observed by Newton was not formed by 
the true sunbeams, but by rays proceeding from 
some bright cloud. In support of these assertions, 
he appeals to frequently repeated experiments on 
the refractions and reflections of light which he 
had exhibited thirty years before to Sir Kenelm 
Digby, " who took notes upon them ;" and he un- 
blushingly states, that, if Newton had used the 
same industry as he did, he would never have 
" taken so impossible a task in hand, as to explain 
the difference between the length and breadth of 
the spectrum by the received laws of refraction." 
When this letter was shown to Newton, he refused 

* This gentleman was the author of a paper in the Philosophical 
Transactions, entitled " Optical Assertions concerning the Rainbow." 
How such a paper could be published by so learned a body seems in the 
present day utterly incomprehensible. The dials which Linus erected 
at Liege, and which were the originals of those formerly in the Priory 
Gardens in London, are noticed in the Philosophical Transactions for 
1703. In one of them the hours were distinguished by touch. 



56 SIR ISAAC NEWTON. 

to answer it ; but a letter was sent to Linus referring 
him to the answer to Pardies, and assuring him that 
the experiments on the spectrum were made when 
there was no bright cloud in the heavens. This 
reply, however, did not satisfy the Dutch experi- 
mentalist. On the 25th February, 1675, he addressed 
another letter to his friend, in which he gravely 
attempts to prove that the experiment of Newton 
was not made in a clear day ; that the prism was 
not close to the hole, and that the length of the 
spectrum was not perpendicular, or parallel to the 
length of the prism. Such assertions could not but 
irritate even the patient mind of Newton. He more 
than once declined the earnest request of Oldenburg 
to answer these observations; he stated, that, as 
the dispute referred to matters of fact, it could only 
be decided before competent witnesses, and he 
referred to the testimony of those who had seen 
his experiments. The entreaties of Oldenburg, how- 
ever, prevailed over his own better judgment, and, 
"lest Mr. Linus should make the more stir," this 
great man was compelled to draw up a long and 
explanatory reply to reasonings utterly contempti- 
ble, and to assertions altogether unfounded. This 
answer, dated November 13th, 1675, could scarcely 
have been perused by Linus, who was dead on the 
15th December, when his pupil Mr. Gascoigne, took 
up the gauntlet, and declared that Linus had shown 
to various persons in Liege the experiment which 
proved the spectrum to be circular, and that Sir 
Isaac could not be more confident on his side 
than they were on the other. He admitted, how- 
ever, that the different results might arise from dif- 
ferent ways of placing the prism. Pleased with the 
" handsome genius of Mr. Gascoigne's letter," New 
ton replied even to it, and suggested that the spec- 
trum seen by Linus may have been the circular one 
formed by one reflexion, or, what he thought more 
probable, the circular one formed by two refraction^ 



CONTROVERSY WITH LUCAS. 57 

and one intervening reflection from the base of the 
prism, which would be coloured if the prism was 

| not an isosceles o^d. This suggestion seems to 

t have enlightened the Dutch philosophers. Mr. Gas- 
coigne, having no conveniences for making the ex- 

( periments pointed out by Newton, requested Mr. 
Lucas of Liege to perform them in his own house. 
This ingenious individual, whose paper gave great 
satisfaction to Newton, and deserves the highest 
praise, confirmed the leading results of the English 

i philosopher ; but though the refracting angle of his 
prism was 60 and the refractions equal, he never 
could obtain a spectrum whose length was more 
thar. from three to three and a half times its breadth, 
while Newton found the length to be Jive times its 
breadth. In our author's reply, he directs his atten- 
tion principally to this point of difference. He 
repeated his measures with each of the three angles 
of three different prisms, and he affirmed that Mr. 
Lucas might make sure to find the image as long or 
longer than he had yet done, by taking a prism with 
plain surfaces, and with an angle of 66 or 67. 
He admitted that the smallness of the angle in Mr. 
Lucas's prism, viz. 60, did not account for the 
shortness of the spectrum which he obtained with 
it ; and he observed in one of his own prisms that 
the length of the image was greater in proportion 
to the refracting angle than it should have been ; an 
effect which he ascribes to its having a greater 
refractive power. There is every reason to believe 
that the prism of Lucas had actually a less disper- 
sive power than that of Newton ; and had the Dutch 
philosopher measured its refractive power instead 
of guessing it, or had Newton been less confident 
than he was* that all other prisms must give a 

* Newton speaks with singular positiveness on this subject. " For / 
know" says he, "that Mr. Lucas's observations cannot hold where the 
refracting angle of the prism is full 60, and the day is clear, and the 
fall length of the colours is measured, and the breadth of the image 
answers to the sun's diameter : and seeing I am well assured of th* 



58 SIR ISAAC NEWTON. 

spectrum of the same length as his in relation to its 
refracting angle and its index of refraction, the in- 
vention of the achromatic telescope would have 
been the necessary result. The objections of Lucas 
drove our author to experiments which he had never 
before made, to measure accurately the lengths of 
the spectra with different prisms of different angles 
and different refractive powers ; and had the Dutch 
philosopher maintained his position with more ob- 
stinacy, he would have conferred a distinguished 
favour upon science, and would have rewarded 
Newton for all the vexation which had sprung from 
the minute discussion of his optical experiments. 

Such was the termination of his disputes with the 
Dutch philosophers, and it can scarcely be doubted 
that it cost him more trouble to detect the origin of 
his adversaries' blunders, than to establish the great 
truths which they had attempted to overturn. 

Harassing as such a controversy must have been 
to a philosopher like Newton, yet it did not touch 
those deep-seated feelings which characterize the 
noble and generous mind. No rival jealousy yet 
pointed the arguments of his opponents ; no charges 
of plagiarism were yet directed against his personal 
character. These aggravations of scientific contro- 
versy, however, he was destined to endure ; and in 
the dispute which he was called to maintain both 
against Hooke and Huygens, the agreeable con- 
sciousness of grappling with men of kindred powers 
was painfully imbittered by the personality and 
jealousy with which it was conducted. 

Dr. Robert Hooke was about seven years older 
than Newton, and was one of the ninety-eight 
original or unelected members of the Royal Society., 

truth and exactness of my own observations, I shall be unwilling to fa' 
diverted by any other experiments from having a fair end made of this 
in the first place." On the supposition that his prism was one of very; 
low dispersive power, Mr. Lucas might, with perfect truth, have usedi 
the very same language towards Newton. 



CHARACTER OF DR. HOOKE. 59 

He possessed great versatility of talent, yet, though 
his genius was of the most original cast, and his 
acquirements extensive, he had not devoted himself 
with fixed purpose to any particular branch of 
knowledge. His numerous and ingenious inven- 
tions, of which it is impossible to speak too highly, 
gave to his studies a practical turn which unfitted 
him for that continuous labour which physical re- 
searches so imperiously demand. The subjects 
of light, however, and of gravitation seem to have 
deeply occupied his thoughts before Newton ap- 
peared in the same field, and there can be no doubt 
that he had made considerable progress in both of 
these inquiries. With a mind less divergent in its 

Eursuits, and more endowed with patience of thought, 
e might have unveiled the mysteries in which both 
these subjects were enveloped, and preoccupied the 
intellectual throne which was destined for his rival ; 
but the infirm state of his health, the peevishness 
of temper which this occasioned, the number of 
unfinished inventions from which he looked both 
for fortune and fame, and, above all, his inordinate 
love of reputation, distracted and broke down the 
energies of his powerful intellect. In the more 
matured inquiries of his rivals he recognised, and 
often truly, his own incompleted speculations ; and 
when he saw others reaping the harvest for which 
he had prepared the ground, and of which he had 
sown the seeds, it was not easy to suppress the 
mortification which their success inspired. In the 
history of science, it has always been a difficult task 
to adjust the rival claims of competitors, when the 
one was allowed to have completed what the other 
was acknowledged to have begun. He who com- 
mences an inquiry, and publishes his results, often 
goes much farther than he has announced to the 
world, and, pushing his speculations into the very 
heart of the subject, frequently submits them to th& 
ear of friendship. From the pedestal of his pub- 



60 SIR ISAAC NEWTON. 

lished labours his rival begins his researches, and 
brings them to a successful issue ; while he has in 
reality done nothing more than complete and de- 
monstrate the imperfect speculations of his prede- 
cessor. To the world, and to himself, he is no 
doubt in the position of the principal discoverer} 
but there is still some apology for his rival when 
he brings forward his unpublished labours ; and some 
excuse for the exercise of personal feeling, when he. 
measures the speed of his rival by his own proximity 
to the goal. 

The conduct of Dr. Hooke would have been 
viewed with some such feeling, had not his arro- 
gance on other occasions checked the natural cur- 
rent of our sympathy. When Newton presented 
his reflecting telescope to the Royal Society, Dr. 
Hooke not only criticised the instrument with undue 
severity, but announced that he possessed an infal- 
lible method of perfecting all kinds of optical instru- 
ments, so that " whatever almost hath been in 
notion and imagination, or desired in optics, may 
be performed with great facility and truth." 

Hooke had been strongly impressed with the 
belief, that light consisted "in the undulations of a 
highly elastic medium pervading all bodies; and, 
guided by his experimental investigation of the phe- 
nomena of diffraction, he had even announced the 
(; great principle of interference, which has performed 
' such an important part in modern science. Regard- 
ing himself, therefore, as in possession of the true 
theory of light, he examined the discoveries of 
Newton in their relation to his own speculative 
views, and, finding that their author was disposed to 
consider that element as consisting of material par- 
ticles, he did not scruple to reject doctrines which 
he believed to be incompatible with truth. Dr. , 
Hooke was too accurate an observer not to admit j 
the general correctness of Newton's observations. ; 
He allowed the existence of different refractions, 






CONTROVERSY WITH HUYGENS. 61 

the unchangeableness of the simple colours, and the 
.production of white light by the union of all the 
polours of the spectrum ; but he maintained that the 
pifferent refractions arose from the splitting and 
rarefying of ethereal pulses, and that there are only 
two colours in nature, viz. red and violet, which pro- 
duce by their mixture all the rest, and which are 
themselves formed by the two sides of a split pulse 
or undulation. 

In reply to these observations, Newton wrote an 
able letter to Oldenburg, dated June 11, 1672, in 
which he examined with great boldness and force 
of argument the various objections of his opponent, 
and maintained the truth of his doctrine of colours, 
as independent of the two hypotheses respecting 
the origin and production of light. He acknow- 
ledged his own partiality to the doctrine of the 
materiality of light ; he pointed out the defects of 
the undulatory theory ; he brought forward new ex- 
periments in confirmati on of his former results ; 
and he refuted the opini >ns of Hooke respecting the 
existence of only two simple colours. No reply 
was made to the powe ul arguments of Newton ; 
and Hooke contented h nself with laying before the 
Society his curious ob? vations on the colours of 
soap-bubbles, and of plates of air, and in pursuing 
his experiments on the diffraction of light, which, 
after an interval of two years, he laid Tbefore the 
same body. 

After he had thus silenced the most powerful of 
his adversaries, Newton was again called upon to 
defend himself against a new enemy. Christian 
Huygens, an eminent mathematician and natural 
philosopher, who, like Hooke, had maintained the 
undulatory theory of light, transmitted to Olden- 
burg various animadversions on the Newtonian doc- 
trine ; but though his knowledge of optics was of 
the most extensive kind, yet his objections were 
nearly as groundless as those of his less enlightened 
F 



62 SIR ISAAC NEWTON, 

countryman. Attached to his own hypothesis re- 
specting the nature of light, namely, to the system 
of undulation, he seems, like Dr. Hooke, to have 
regarded the discoveries of Newton as calculated to 
overturn it ; but his principal objections related tc 
the composition of colours, and particularly of white 
light, which he alleged could be obtained from the 
union of two colours, yellow and blue. To this and 
^similar objections, Newton replied that the colours 
in question were not simple yellows and blues, but 
were compound colours, in which, together, all the 
colours of the spectrum were themselves blended ; 
and though he evinced some strong traces of feeling 
at being again put upon his defence, yet his high 
respect for Huygens induced him to enter with 
patience on a fresh development of his doctrine. 
Huygens felt the reproof which the tone of this 
answer so gently conveyed, and in writing to Olden- 
burg, he used the expression, that Mr. Newton 
" maintained his doctrine with some concern." To 
this our author replied, " As for Mr. Huygens's ex- 
pression, I confess it was a little ungrateful to me, 
to meet with objections which had been answered 
before, without having the least reason given me 
why those answers were insufficient." But though 
Huygens appears in this controversy as a rash 
objector to the Newtonian doctrine, it was after- 
ward the fate of Newton to play a similar part 
against the Dutch philosopher. When Huygens 
published his beautiful law of double refraction in 
Iceland spar, founded on the finest experimental 
analysis of the phenomena, though presented as a 
result of the undulatory system, Newton not only 
rejected it, but substituted for it another law entirely 
inconsistent with the experiments of Huygens, which 
Newton himself had praised, and with those of all 
succeeding philosophers. 

The influence of these controversies on the mind 
of Newton seems to have been highly exciting 



REFRACTING TELESCOPES. 63 

Even the satisfaction of humbling all his antago- 
nists he did not feel as a sufficient compensation 
for the disturbance of his tranquillity. " 1 intend," 
says he,* " to be no farther solicitous about matters 
of philosophy. And therefore I hope you will not 
take it ill if you find me never doing any thing more 
in that kind ; or rather that you will favour me in 
my determination, by preventing, so far as you can 
conveniently, any objections or other philosophical 
letters that may concern me." In a subsequent let- 
ter in 1675, he says, " I had some thoughts of writing 
a further discourse about colours, to be read at one 
of your assemblies ; but find it yet against the grain 
to put pen to paper any more on that subject ;" and 
in a letter to Leibnitz, dated December the 9th, 1675, 
lie observes, " I was so persectited with discussions 
arising from the publication of my theory of light, 
that I blamed my own imprudence for parting with 
so substantial a blessing as my quiet to run after a 
shadow." 



CHAPTER V. 

Mistake of Newton in supposing that the Improvement nf Refracting 
Telescopes was hopeless Mr. Hall invents the Achromatic Telescope 
Principles of the Achromatic Telescope explained // is re-invented 
by Dollond, and improved by future Artists Dr. Blair's Aplanatie 
Telescope Mistakes in Newton's Analysis of the Spectrum Modern 
Discoveries respecting the Structure of the Spectrum. 

THE new doctrines of the composition of light, 
and of the difTerent refrangibility of the rays which 
compose it, having been thus established upon an 
impregnable basis, it will be interesting to take a 
general view of the changes which they have under- 

I etter to Oldenburg in 1672, containing his first reply to Huygens. 



64 SIR ISAAC NEWTON. 

gone since the time of Newton, and of their influ- 
ence on the progress of optical discovery. 

There is no fact in the history of science more 
singular than that Newton should have believed 
that all bodies produced spectra of equal length, or 
separated the red and violet rays to equal distances 
when the refraction of the mean rays was the 
same. This opinion, unsupported by experiments, 
and not even sanctioned by any theoretical views, 
seems to have been impressed upon his mind with 
all the force of an axiom.* Even the shortness of 
the spectrum observed by Lucas did not rouse him 
to further inquiry ; and when, under the influence 
of this blind conviction he pronounced the improve- 
ment of the refracting telescope to be desperate, he 
checked for a long time the progress of this branch 
of science, and furnished to future philosophers a 
lesson which cannot be too deeply studied. 

In 1729, about two years after the death of Sir 
Isaac, an individual unknown to science broke the 
spell in which the subject of the spectrum had been 
so singularly bound. Mr. Chester More Hall, of 
More Hall in Essex, while studying the mechanism 
of the human eye, was led to suppose that tele- 
scopes might be improved by a combination of 
lenses of different refractive powers, and he actually 
completed several object-glasses upon this principle. 
The steps by which he arrived at such a construc- 
tion have not been recorded ; but it is obvious that 
he must have discovered what escaped the sagacity 
of Newton, that prisms made of different kinds of 

* In an experiment made by Newton, he had occasion to counteract 
the refraction of a prism of glass by another prism of water ; and had 
he completed the experiment, and studied the result of it, he could not 
have failed to observe a quantity of uncorrected colour, which would 
haTO led him to the discovery of the different dispersive powers of bodies. 
But in order to increase the refractive power of the water, he mixed 
with it a little sugar of lead, the high dispersive power of which seems 
to have rendered the dispersive power of the water equal to that of ihe 
glass, and thus to have corrected the uncompensated colour of the glass 
prism. 



ACHROMATIC TELESCOPE. 



66 



produced different degrees of separation of the 
red and violet rays, or gave spectra of different 
lengths when the refraction of the middle ray of the 
spectrum was the same. 

In order to explain how such a property led him 
to the construction of a telescope without colour, or 
an achromatic telescope, let us take a lens LL of 
crown or plate glass, whose focal length LY is 
about twelve inches. When the sun's rays SL, 



Fig. 6. 




SL fall upon it, the red will be refracted to R, the 
yellow to Y, and the violet to V. If we now place 
behind it a concave lens II of the same glass, and 
of the same focus or curvature, it will be found, 
both by experiment and by drawing the refracted 
rays, according to the rules given in elementary 
works, that the concave glass // will refract the 
rays LR, LR into LS', LS ; , and the rays LV, LV 
into LS', LS' free of all colour; but as these rays 
will be parallel, the two lenses will not have a 
focus, and consequently cannot form an image so 
as to be used as the object-glass of a telescope. 
This is obvious from another consideration ; for 
since the curvatures of the convex and concave 
lenses are the same, the two put together will be 
exactly the same as if they were formed out of a 
single piece of glass, having parallel surfaces like a 
watch-glass, so that the parallel rays of light SL, 
F2 



66 SIR ISAAC NEWTON. 

SL will pass on in the same direction LS', LS* 
affected by equal and opposite refractions as in a 
piece of plane glass. 

Now, since the convex lens LL separated the 
white light SL, SL into its component coloured 
rays, LV, LV being the extreme violet, and LR 
LR the extreme red ; it follows that a similar con- 
cave lens of the same glass is capable of uniting 
into white light LS', LS' rays, as much separated 
as LV, LR are. Consequently, if we take a con- 
cave lens II of the same, or of a greater refractive 
power than the convex one, and having the power 
of uniting rays farther separated than LV, LR are, 
a less concavity in the lens II will be sufficient to 
unite the rays LV, LR into a white ray LS' ; but 
as the lens // is now less concave than the lens LL 
is convex, the concavity will predominate, and the 
uncoloured rays LS', LS' will no longer be parallel, 
but will converge to some point 0, where they will 
form a colourless or achromatic image of the sun. 

The effect now described may be obtained by 
making the convex lens LL of crown or of plate 
glass, and the concave one of flint glass, or that of 
which wineglasses are made. If the concave lens 
// has a greater refractive power than LL, which is 
always the case, the only effect of it will be to 
make the rays converge to a focus more remote 
than O, or to render a less curvature necessary in 
//, if O is fixed for the focus of the combined lenses. 

Such is the principle of the achromatic telescope 
as constructed by Mr. Hall. This ingenious indi- 
vidual employed working opticians to grind his 
lenses, and he furnished them with the radii of the 
surfaces, which were adjusted to correct the aber- 
ration of figure as well as of colour. His invention, 
therefore, was not an accidental combination of a 
convex and a concave lens of different kinds of 
glass, which might have oeen made merely for ex- 
periment; but it was a complete achromatic tele- 



ACHROMATIC TELESCOPES. 67 

scope, founded on a thorough knowledge of the 
lifferent dispersive powers of crown and flint glass. 
[t is a curious circumstance, however, in the his- 
;ory of the telescope, that this invention was ac- 
tually lost. Mr. Hall never published any account 
(}f his labours, and it is probable that he kept them 
secret till he should be able to present his instru- 
nent to the public in a more perfect form ; and it 
,vas not till John Dollond had discovered the pro- 
perty of light upon which the instrument depends, 
md had actually constructed many fine telescopes, 
;hat the previous labours of Mr. Hall were laid be- 
bre the public.* From this period the achromatic 
elescope underwent gradual improvement, and by 
he successive labours of Dollond, Ramsden, Blair, 
Pulley, Guinand, Lerebours, and Fraunhofer, it has 
>ecome one of the most valuable instruments in. 
)hysical science. 

Although the achromatic telescope, as constructed 
>y Dollond, was founded on the principle that the 
spectra formed by crown and flint glass differed 
mly in their relative lengths, when the refraction 
)f the mean ray was the same, yet by a more mi- 
lute examination of the best instruments, it was 
bund that they exhibited white or luminous objects 
inged on one side with a green fringe, and on the 
Hher with one of a claret colour. These colours, 
tvhich did not arise from any defect of skill in the 
.rtist, were found to arise from a difference in the 
extent of the coloured spaces in two equal spectra 
'ormed by crown and by flint glass. This property 
was called the irrationality of the coloured spaces, 
and the uncorrected colours which remained when 
;he primary spectrum of the crown glass was cor* 
rected by the primary spectrum of the flint glass 
were called the secondary or residual spectrum. By 

* See the article OPTICS in the Edinburgh Encyclopedia, vol xv 
479, note. 



68 SIR ISAAC NEWTON. 

a happy contrivance, which it would be out of placi 
here to describe, Dr. Blair succeeded in correcting 
this secondary spectrum, or in removing the greer 
and claret-coloured fringes which appeared in th< 
best telescopes, and to this contrivance he gave the 
name of the Aplanatic Telescope. 

But while Newton thus overlooked these remark 
able properties of the prismatic spectrum, as formec 
by different bodies, he committed some considera- 
ble mistakes in his examination of the spectrurr 
which was under his own immediate examination 
It does not seem to have occurred to him that the 
relations of the coloured spaces must be greatly 
modified by the angular magnitude of the sun or the 
luminous body, or aperture from which the spec- 
trum is obtained ; and misled by an apparent ana- 
logy between the length of the coloured spaces anc 

,the divisions of a musical chord,* he adopted the 

'j: latter, as representing the proportion of the col- 
oured spaces in every beam of white light. Hac 
two other observers, one situated in Mercury, anc 
the other in Jupiter, studied the prismatic spectrurr. 
of the sun by the same instruments, and with the 
same sagacity as Newton, it is demonstrable thai 
they would have obtained very different results. Or 
account of the apparent magnitude of the sun in Mer- 
cury, the observer there would obtain a spectrum 
entirely without green, having red, orange, and yel- 

>low at one end, the white in the middle, and termi- 
nated at the other end with blue and violet. The 

'observer in Jupiter would, on the contrary, have 
obtained a spectrum in which the colours were 
much more condensed. On the planet Saturn a 
spectrum exactly similar would have been obtained, 

*"This result was obtained," as Newton says, "by an assistanl 
whose eyes were more critii al than mine, and who, by right lines drawn 
across the spectrum, noted the confines of the colours. And this opera- 
tion being divers times repeated both on the same and on several papers, 
I found that the observations agreed well enough with one another." 
OPTICS, Part II. Book III. 



PRISMATIC SPECTRUM. 69 

withstanding the greater diminution of the sun's 
[apparent diameter* It may now be asked, which of 
all these spectra are we to consider as exhibiting 
the number, and arrangement, and extent of the 
coloured spaces proper to be adopted as the true 
[analysis of a solar ray. 

The spectrum observed by Newton has surely no 
claim to our notice, merely because it was observed 
upon the surface of the earth. The spectrum ob- 
tained in Mercury affords no analysis at all of the 
incident beam, the colours being almost all com- 
pound, and not homogeneous, and that of Newton 
is liable to the same objection. Had Newton ex- 
amined his spectrum under the very same circum- 
stances in winter and in summer, he would have 
found the analysis of the beam more complete in 
summer, on account of the diminution of the sun's 
diameter ; and, therefore, we are entitled to say that i 
neither the number nor the extent of the coloured/ 
spaces, as given by Newton, are those which belong! 
fohomogeneous and uncompoundedjight. [ 

'I'tie spectrum obtained in Jupiter and Saturn is 
the only one where the analysis is complete, as it is 
incapable of having its character altered by any far- 
ther diminution of the sun's diameter. Hence we 
are forced to conclude, not only that the number 
and extent of the primitive homogeneous colours, 
as given by Newton, are incorrect ; but that if he had 
attempted to analyze some of the primitive tints in 
the spectrum, he would have found them decidedly 
composed of heterogeneous rays. There is one 
consequence of these observations which is some- 
what interesting. A rainbow formed in summer, 
when the sun's diameter is least, must have its col- 
ours more condensed and homogeneous than in win- 
ter, when the size of its disk is a maximum, and 
when the upper or the under limb of the sun is 
eclipsed, a rainbow formed at that time will lose 
entirely the yellow rays, and have the green and the 



70 SIR ISAAC NEWTON. 

red in perfect contact. For the same reason, a rain- ] 
bow formed in Venus and Mercury will be destitute 
of green rays, and have a brilliant bow of white 
light separating two coloured arches ; while in Mars 
Jupiter, Saturn, and the Georgian planet, the bo\\ 
will exhibit only four homogeneous colours. 

From his analysis of the solar spectrum, Newtor 
concluded, " that to the same degree of refrangibilit} 
ever belonged the same colour, and to the same 
colour ever belonged the same degree of refrangi- 
bility ;" and hence he inferred, that red, orange, yel- 
low, green, blue, indigo, and violet were primary and. 
simple colours. He admitted, indeed, that "the 
same colours in specie with these primary ones ma); 
be also produced by composition. For a mixture of 
yellow and blue makes green, and of red and yellou 
makes orange;" but such compound colours were 
easily distinguished from the simple colours of the 
spectrum by the circumstance, that they are always 
capable of being resolved by the action of the prism 
into the two colours which compose them. 

This view of the composition of the spectrum 
might have long remained unchallenged, had we not 
been able to apply to it a new mode of analysis. 
Though we cannot separate the green rays of the 
spectrum into yellow and blue by the refraction of 

grisms, yet if we possessed any substance which 
ad a specific attraction for blue rays, and which 
stopped them in their course, and allowed the yel- 
low rays to pass, we should thus analyze the green 
as effectually as if they were separated by refraction. 
The substance which possesses this property is a 
purplish blue glass, similar to that of which finger- 
glasses are made. When we view through a piece 
of this glass, about the twentieth of an inch thick, 
a brilliant prismatic spectrum, we find that it has 
exercised a most extraordinary absorptive action on 
the different colours which compose it. The red 
part of the spectrum is divided into two red spaces^ 



SPECTRUM OF THREE COLOURS. 71 

separated by an interval entirely devoid of light. 
e Next to the inner red space comes a space of bright 
oi/ellow, separated from the red by a visible interval. 
;, A.fter the yellow comes the gr&m, with an obscure 
rjspace between them, then follows the blue and the 
biolet, the last of which has suffered little or no 
Diminution. Now it is very obvious, that in this 
Jbxperiment, the blue glass has actually absorbed 
phe red rays, which, when mixed with the yellow 
an one side, constituted orange, and the blue rays, 
which, when mixed with the yellow on the other 
side, constituted green, so that the insulation of 
;he yellow rays thus effected, and the disappearance 
)f the orange, and of the greater part of the green 
light, proves beyond a doubt that the orange and 
rreen colours in the spectrum are compound col- 
>urs, the former consisting of red and yellow rays, 
md the latter of yellow and blue rays of the very 
ame refrangibility. If we compare the two red 
spaces of the spectrum seen through the blue glass 
kvith the red space seen without the blue glass, it 
vill be obvious that the red has experienced such 
in alteration in its tint by the action of the blue 
flass, as would be effected by the absorption of a 
imall portion of yellow rays ; and hence we con- 
dude, that the red of the spectrum contains a slight 
inge of yellow, and that the yellow space extends 
>ver more than one-half of the spectrum, including 
he red, orange, yellow, green, and blue spaces. 

I have found also that red light exists in the yel- 
ow space, and it is certain that in the violet space 
ed light exists in a state of combination with the 
)lue rays. From these and other facts which it 
ivould be out of place here to explain, I conclude 
hat the prismatic spectrum consists of three differ- 
nt spectra, viz. red, yellow, and blue, all having 
he same length, and all overlapping each other. 
Hence red, yellow, and blue rays of the very same 
efrangibility coexist at every point of the spec* 



72 em ISAAC NEWTON. 

trum ; but the colour at any one point will be thai 
of the predominant ray, and will depend upon the 
relative distance of the point from the maximum 
ordinate of the curve which represents the intensity 
of the light of each of the three spectra. 

This structure of the spectrum, which harmo- 
nizes with the old hypothesis of three simple colours, 
will be understood from the annexed diagram 
where MN is the spectrum of seven colours, al 
compounded of the three simple ones, red, yellow 

Fig. 7. 




and blue. The ordinates of the curves R, Y, anc 
B will express the intensities of each colour at dif- 
ferent points of the spectrum. At the red extrem- 
ity M of the spectrum, the pure red is scarcel} 
altered by the very slight intermixture of yellow 
and blue. Farther on in the red space, the yellou 
begins to make the red incline to scarlet. It ther 
exists in sufficient quantity to form orange, and, as 
the red declines, the yellow predominates over the 
feeble portion of red and blue which are mixed wit! 
it. As the yellow decreases in intensity, the in- 
creasing blue forms with it a good green, and the 
blue rising to its maximum speedily overpowers the 
small portion of yellow and red. When the blue 
becomes very faint, the red exhibits its influence 
in converting it into violet, and the yellow ceasei 



LIXES IN THE SPECTRtTM. 73 

to exercise a marked influence on the tint. The 
influence of the red over the blue space is scarcely 
perceptible, on account of the great intensity of the 
blue light ; but we may easily conceive it to reap- 
pear and form the violet light, not only from the 
rapid decline of the blue light, but from the greater 
influence of the red rays upon the retina. 

These views may, perhaps, be more clearly under- 
stood by supposing that a certain portion of white 
light is actually formed at every point of the spec- 
trum by the union of the . requisite number of the 
three coloured rays that exist at any point. The 
white light thus formed will add to the brilliancy 
without affecting the tint of the predominant colour. 

In the violet space we may conceive the small 
portion of yellow which exists there to form white 
light with a part of the blue and a part of the red, 
so that the resulting tint will be violet, composed 
of the blue and the small remaining portion of red, 
mixed with the white light. This white light will 
possess the remarkable property of not being sus- 
ceptible of decomposition by the analysis of the 
prism, as it is composed of red, yellow, and blue 
rays of the very same refrangibility. The insula- 
tion of this white light by the absorption of the 
predominant colours I have effected in the green, 
yellow, and red spaces, and by the use of new ab- 
sorbing media we may yet hope to exhibit it in some 
of the other colours, particularly in the brightest 
part of the blue space, where an obvious approxi- 
mation to it takes place. 

: Among the most important modern discoveries 
respecting the spectrum we must enumerate that 
of fixed dark and coloured lines, which we owe to 
the sagacity of Dr. Wollaston and M. Fraunhofer. 
Two or three of these lines were discovered by Dr. 
Wollaston, but nearly 600 have been detected by 
means of the fine prisms and the magnificent appa- 
ratus of the Bavarian optician. These lines are 
G 



SIR ISAAC NEWTOW. 



parallel to one another, and perpendicular to the 
length of the spectrum. The largest occupy a 
space from 5" to 10" in breadth. Sometimes they 
occur in well-defined lines, and at other times in 
groups ; and in all spectra formed from solar light, 
they preserve the same order and intensity, and the 
same relative position to the coloured spaces, what- 
ever be the nature of the prism by which they are 
froduced. Hence these lines are fixed points, by 
which the relative dispersive powers of different 
media may be ascertained with a degree of accu- 
racy hitherto unknown in this branch of science. In 
the light of the fixed stars, and in that of artificial 
flames, a different system of lines is produced, and 
this system remains unaltered, whatever be the na- 
ture of the prism by which the spectrum is formed. 
The most important fixed lines in the spectrum 
formed by light emitted from the sun, whether it is 
reflected from the sky, the clouds, or the moon, may 
be easily seen by looking at a narrow slit in the 
window-shutter of a dark room, through a hollow 
prism formed of plates of parallel glass, and filled 
with any fluid of a considerable dispersive power. 
The slit should not greatly exceed the twentieth of 
an inch, and the eye should look through the thinnest 
edge of the prism where there is the least thickness 
of fluid. These lines I have found to be the boun- 
daries of spaces within which the rays have par- 
ticular affinities for particular bodies. 



COLOURS OF THIN PLATES. 75 



CHAPTER VL 

Colours of thin Plates first studied by Boy ^and Hooke Newton de- 
termines the Law of their Production His Theory of Fits of Easy 
Refection and Transmission Colours of thick Plates. 

IN examining the nature and origin of colours as 
the component parts of white light, the attention of 
Newton was directed to the curious subject of the 
colours of thin plates, and to its application to ex- 
plain the colours of natural bodies. His earliest 
researches on this subject were communicated, in 
his Discourse on Light and Colours, to the Royal 
Society, on the 9th December, 1675, and were read 
at subsequent meetings of that body. This discourse 
contained fuller details respecting the composition 
and decomposition of light than he had given in his 
letter to Oldenburg, and was concluded with nine 
propositions, showing how the colours of thin trans- 
parent plates stand related to those of all natural 
bodies. 

The colours of thin plates seem to have been 
first observed by Mr. Boyle. Dr. Hooke afterward 
studied them with some care, and gave a correct 
account of the leading phenomena, as exhibited in 
the coloured rings upon soap-bubbles, and between 
plates of glass pressed together. He recognised 
that the colour depended upon some certain thick- 
ness of the transparent plate, but he acknowledges 
that he had attempted in vain to discover the rela- 
tion between the thickness of the plate and the 
colour which it produced. 

Dr. Hooke succeeded in splitting a mineral sub- 
stance, called mica, into films of such extreme thin- 
ness as to give brilliant colours. One p'ate, for ex- 



76 SIR ISAAC NEWTON. 

ample, gave a yellow colour, another a blue colour, 
and the two together a deep purple ; but, as plates 
which produced those colours were always less than 
the 12,000th part of an inch thick, it was quite im- 
practicable, by any contrivance yet discovered, to 
measure their thickness, and determine the law ac- 
cording to which the colour varied with the thick- 
ness of the film. Newton surmounted this difficulty 
by laying a double convex lens, the radius of curva- 
ture of each side of which was fifty feet, upon the 
flat surface of a plano-convex object-glass, and in 
this way he obtained a plate of air or of space vary- 
ing from the thinnest possible edge at the centre of 
the object-glass where it touched the plane surface, 
to a considerable thickness at the circumference of 
the lens. When light was allowed to fall upon the 
object-glass, every different thickness of the plate 
of air between the object-glass gave different colours, 
so that the point where the two object-glasses 
touched one another was the centre of a number of 
concentric coloured rings. Now, as the curvature 
of the object-glass was known, it was easy to cal- 
culate the thickness of the plate of air at which any 
particular colour appeared, and thus to determine 
the law of the phenomena. 

In order to understand how he proceeded, let 
CED be the convex surface of the one object-glass, and 
AEB the flat surface of the other. Let them touch 
at the point E, and let homogeneous red rays fall 
upon them, as shown in the figure. At the point 
of contact E, where the plate of air is inconceiva- 
bly thin, not a single ray of the pencil RE is re- 
flected. The light is w r holly transmitted, and, con- 
sequently, to an eye above E, there will appear at 
E a black spot. At <z, where the plate of air is 
thicker, the red light ra is reflected in the direction 
ca', and as the air has the same thickness in a circle 
round tho point E, the eye above E, at a, will see 
next the black spot E a ring of red light. At m, 



COLOURS OF THIN PLATES. 

Fig. 8. 



77 




where the thickness of the air is a little greater than 
at , the light r'm is all transmitted as at E, and not 
a single ray suffers reflection, so that to an eye 
above E at m f there will be seen without the red ring 
a a dark ring m. In like manner, at greater thick- 
nesses of the plate of air, there is a succession of 
red and dark rings, diminishing in breadth as shown 
in the diagram. 

When the same experiment was repeated in orarige, 
yellow, green, Uue, indigo, and violet light, the very 
same phenomenon was observed; with this differ- 
ence only, that the rings were largest in red light, 
and smallest in violet light, and had intermediate 
magnitudes in the intermediate colours. 

If the observer now places his eye below E, so 
as to see the transmitted rays, he will observe a set 
of rings as before, but they will have a bright spot 
in their centre at E, and the luminous rings will now 
correspond with those which were dark when seen 
by reflection, as will be readily understood from in- 
specting the preceding diagram. 

When the object-glasses are illuminated by white 
G2 



78 SIR ISAAC NEWTON. 

light, the seven systems of rings, formed by all the 
seven colours which compose white light, will now 
be seen at once. Had the rings in each colour been 
all of the same diameter they would all have formed 
brilliant white rings, separated by dark intervals; 
but, as they have all different diameters, they will 
overlap one another, producing rings of various 
colours by their mixture. These colours, reckoning 
from the centre E, are as follows : 

1st Order. Black, blue, white, yellow, orange, red. 

2d Order. Violet, blue, green, yellow, orange, red. 

3d Order. Purple, blue, green, yellow, red, bluish- 
red. 

4th Order. Bluish-green, green, yellowish-green, 
red. 

5th Order. Greenish-blue, red. 

6th Order. Greenish-blue, red. 

By accurate measurements, Sir Isaac found that 
the thicknesses of air at which the most luminous 
parts of the first rings were produced, were in parts 
of an inch TT f 3-^, -py^Tnnj? TT5Tr<nr TTffrnnr* 



c TT f 3-^, -py^Tnnj? TT5Tr<nr TTffrnnr* TT^ffw* 
If tne niedium or the substance of the thin 
plate is water, as in the case of the soap-bubble, 
which produces beautiful colours according to its 
different degrees of thinness, the thicknesses at 
which the most luminous parts of the rings appear 
are produced at j.^ of the thickness at which they 
are produced in air, and in the case of glass or mica 
at r.?V? f tnat thickness; the numbers 1.336, 1.525 
expressing the ratio of the sines of the angles of 
incidence and refraction in the substances which 
produce the colours. 

From the phenomena thus briefly described, Sir 
Isaac Newton deduces that ingenious, though hy- 
pothetical, property of light, called its fits of easy 
reflection and transmission. This property consists in 
supposing that every particle of light from its first 
discharge from a luminous body possesses, at equally 
distant intervals, dispositions to be reflected from, 



FITS OF REFLECTION, ETC 79 

and transmitted through, the surfaces of bodies upon 
which it is incident. Hence, if a particle of light 
reaches a reflecting surface of glass when it is in 
its^ of reflection, or in its disposition to be reflected, 
it will yield more readily to the reflecting force of 
the surface ; and, on the contrary, if it reaches the 
same surface while in a Jit of easy transmission, or 
in a disposition to be transmitted, it will yield with 
more difficulty to the reflecting force. Sir Isaac 
has not ventured to inquire into the cause of this 
property ; but we may form a very intelligible idea 
of it by supposing, that the particles of light have 
two attractive and two repulsive poles at the ex- 
tremities of two axes at right angles to each other, 
and that the particles revolve round their axes, and 
at equidistant intervals bring one or other of these 
axes into the line of the direction in which the par- 
ticle is moving. If the attractive axis is in the line 
of the direction in which the particle moves when it 
reaches the refracting surface, the particle will yield 
to the attractive force of the medium, and be re- 
fracted and transmitted ; but if the repulsive axis is 
in the direction of the particle's motion when it 
reaches the surface, it will yield to the repulsive 
force of the medium, and be reflected from it. 

The application of the theory of alternate fits of 
reflection and transmission to explain the colours of 
thin plates is very simple. When the light falls upon 
the first surface AB, Fig. 8 of the plate of air be- 
tween AB and CED, the rays that are in a fit of re- 
flection are reflected, and those that are in a fit of 
transmission are transmitted. Let us call F the 
length of a fit, or the distance through which the 
particle of light moves while it passes from the state 
of being in a fit of reflection to the state of being in 
a fit of transmission. Now, as all the particles of 
light transmitted through AB were in a state of easy 
transmission when they entered AB, it is obvious, 
that, if the plate of air at E is so thin as to be less 



80 SIR ISAAC NEWTON. 

than one-half of F, the particles of light will still 
be in their disposition to be transmitted, and conse- 
quently the light will be all transmitted, and none 
reflected at the curve surface at E. When the plate 
becomes thicker towards 0, so that its thickness ex- 
ceeds half of F, the light will not reach the surface 
CE till it has come under its fit of reflection, and 
consequently at a the light will be all reflected, and 
none transmitted. As the thickness increases to- 
wards m, the light will have come under its fit of 
transmission, and so on, the light being reflected at 
a, Z, and transmitted at E, m. This will perhaps be 
still more easily understood from fig. 9, where we 

Fig. 9. 




may suppose AEG to be a thin wedge of glass or 
any other transparent body. When light is incident 
on the first surface AE, all the particles of it that 
are in a fit of easy reflection will be reflected, and 
all those in a fit of easy transmission will be trans- 
mitted. As the fits of transmission all commence 
at AE, let the first fit of transmission end when the 
particles of light have reached ab, and the second 
when they have reached ef; and let the fits of re- 
flection commence at cd and gh. Then, as the fit 
of transmission continues from AE to ab, all the 
light that falls upon the portion mE of the second 
surface will be transmitted and none reflected, so 
that to an eye above E the space mE will appear 
black. As the fit of reflection commences at ab, and 



COLOURS OF THICK PLATES. 81 

continues to cd, all the light which falls upon the 
portion nm will be reflected, and none transmitted ; 
and so on, the light being transmitted at mE and 
pn, and reflected at nm and qp. Hence to an eye 
above E the wedge-shaped film of which AEG is 
a section will be covered with parallel bands or 
fringes of light separated by dark fringes of the 
same breadth, and they will be all parallel to the 
thin edge of the plate, a dark fringe corresponding 
10 the thinnest edge. To an eye placed below CE 
similar fringes will be seen, but the one correspond- 
ing to the thinnest edge mE will be luminous. 

If the thickness of the plate does not vary accord- 
ing to a regular law as in Jig. 9, but if, like a film of 
blown glass, it has numerous inequalities, then the 
alternate fringes of light and darkness will vary with 
the thickness of the film, and throughout the whole 
length of each fringe the thickness of the film will 
be the same. 

We have supposed in the preceding illustration 
that the light employed is homogeneous. If it is 
white, then the differently coloured fringes will form 
by their superposition a system of fringes analogous 
to those seen between two object-glasses, as already 
explained. 

The same periodical colours which we have now 
described as exhibited by thin plates were discov- 
ered by Newton in thick plates, and he has ex- 
plained them by means of the theory of fits ; but it 
would lead us beyond the limits of a popular work 
like this to enter into any details of his observations, 
or to give an account of the numerous and important 
additions which this branch of optics has received 
from the discoveries of deseeding authors. 



SIR ISAAC NEWTON. 



CHAPTER VII. 

Newton's Theory of the Colours of Natural Bodies explained Objec- 
tions to it stated New Classification of Colours Outline of a New 
Theory proposed, 

IP the objects of the material world" had been 
illuminated with white light, all the particles of 
which possessed the same degree of refrangibility, 
and were equally acted upon by the bodies on which 
they fall, all nature would have shone with a leaden 
hue, and all the combinations of external objects, 
and all the features of the human countenance, would 
have exhibited no other variety but that which they 
possess in a pencil sketch or a China-ink drawing. 
The rainbow itself would have dwindled into a nar- 
row arch of white light, the stars would have shone 
through a gray sky, and the mantle of a wintry 
twilight would have replaced the golden vesture of 
the rising and the setting sun. But He who has ex- 
hibited such matchless skill in the organization of 
material bodies, and such exquisite taste in the forms 
upon which they are modelled, has superadded that 
ethereal beauty which enhances their more per- 
manent qualities, and presents them to us in the 
ever-varying colours of the spectrum. Without this 
the foliage of vegetable life might have rilled the eye 
and fostered the fruit which it veils, but the youth- 
ful green of its spring would have been blended with 
the dying yellow of its autumn. Without this the 
diamond might have displayed to science the beauty 
of its forms, and yielded to the arts its adamantine 
virtues ; but it would have ceased to shine in the 
chaplet of beauty, and to sparkle in the diadem of 
princes. Without this the human countenance might 



COLOURS OF NATURAL BODIES. 83 

have expressed all the sympathies of the heart, but 
the " purple light of love" would not have risen on 
the cheek, nor the hectic flush been the herald of 
its decay. 

The gay colouring- with which the Almighty has 
decked the pale marble of nature is not the result 
of any quality inherent in the coloured body, or in 
the particles by which it may be tinged, but is merely 
a property of the light in which they happen to be 
Dlaced. Newton was the first person who placed 
his great truth in the clearest evidence. He found 
hat all bodies, whatever were their peculiar colours, 
exhibited these colours only in white light. When 
hey were illuminated by homogeneous red light 
hey appeared red, by homogeneous yellow light, 
jellow, and so on, " their colours being most brisk 
and vivid under the influence of their own daylight 
colours." The leaf of a plant, for example, ap- 
)eared green in the white light of day, because it 
lad the property of reflecting that light in greater 
abundance than any other. When it was placed in 
lomogeneous red light, it could no longer appear 
green, because there was no green light to reflect ; 
nit it reflected a portion of red light, because there 
was some red in the compound green which it had 
;he property of reflecting. Had the leaf originally 
reflected a pure homogeneous green, unmixed with 
red, and reflected no white light from its outer sur- 
face, it would have appeared quite black in pure ho- 
mogeneous red light, as this light does not contain 
a single ray which the leaf was capable of reflect- 
ing. Hence the colours of material bodies are owing 
to the property which they possess of stopping cer- 
tain rays of white light, while they reflect or trans- 
mit to the eye the rest of the rays of which white 
light is composed. 

So far the Newtonian doctrine of colours is ca- 
pable of rigid demonstration; but its author was 
not content with carrying it thus far : he sought to 



84 SIR ISAAC NEWTON. 

determine the manner in which particular rays are 
stopped, while others are reflected or transmitted ; 
and the result of this profound inquiry was his theory 
of the colours of natural bodies, which was commu- 
nicated to the Royal Society on the 10th February, 
1675. This theory is perhaps the loftiest of all his 
speculations ; and though, as a physical generaliza- 
tion, it stands on a perishable basis, and must soon 
be swept away in the progress of science, it yet 
bears the deepest impress of the grasp of his pow- 
erful intellect. 

The principles upon which this theory is founded 
are the following : 

1. Bodies that have the greatest refractive powers 
reflect the greatest quantity of light; and at the 
confines of equally refracting media there is no re- 
flection. 1 

2. The least particles of almost all natural bodies 
are in some measure transparent. 

3. Between the particles of bodies are many pores 
or spaces, either empty or filled with media of less 
density than the particles. 

4. The particles of bodies and their pores, or the 
spaces between the particles, have some definite 
size. 

Upon these principles Newton explains the origin 
of transparency, opacity, and colour. 

Transparency^ considers as arising from the par- 
ticles and their intervals or pores being too small to 
cause reflection at their common surfaces,* so that 
all the light which enters transparent bodies passes 
through them without any portion of it being turned 
from its path by reflection. If we could obtain, for 
example, a film of mica whose thickness does not 
exceed two-thirds of the millionth part of an inch, 
all the light which fell upon it would pass through it 
and none would be reflected. If this film was thei] 

* Optics, Book ii. Prop. iv. 



COLOURS OF NATURAL BODIES. 85 

cut into fragments, a number of such fragments 
would constitute a bundle, which would also trans- 
mit all the light which fell upon it, and be perfectly 
transparent. 

Opacity in bodies arises, he thinks, from an oppo- 
site cause, viz. when the parts of bodies are of such 
a size as to be capable of reflecting the light which 
falls upon them, in which case the light is "stopped 
or stifled" by the multitude of reflections. 

The colours of natural bodies have, in the New- 
tonian hypothesis, the same origin as the colours of 
thin plates, their transparent particles, according to 
their several sizes, reflecting rays of one colour, and 
transmitting those of another. "For if a thinned 
or plated body which, being of an uneven thickness, 
appears all over of one uniform colour, should be slit 
into threads, or broken into fragments of the same 
thickness with the plate or film, every thread or frag- 
ment should keep its colour, and consequently, a 
heap of such threads or fragments should constitute 
a mass or powder of the same colour which the 
plate exhibited before it was broken: and the parts 
of all natural bodies being like so many fragments 
of a plate, must, on the same grounds, exhibit the 
same colour." 

Such is the theory of the colours of natural 
bodies, stated as clearly and briefly as we can. It 
has been very generally admitted by philosophers, 
both of our own and of other countries, and has been 
recently illustrated and defended by a French philoso- 
pher of distinguished eminence. That this theory 
affords the true explanation of certain colours, or, 
to speak more correctly, that certain coloms in natu- 
ral bodies are the colours of thin plates, cannot be 
doubted; but it will not be difficult to show that it is 
quite inapplicable to that great class of phenomena 
which may be considered as representing the colours 
of natural bodies. 

The first objection to the Newtonian theory is the 
H 



86 SIR ISAAC NEWTON. 

total absence of all reflected light from the particles 
of transparent coloured media, such as coloured 
gems, coloured glasses, and coloured fluids. This 
objection was urged long ago by Mr. Delaval, who 
placed coloured fluids on black grounds, and never 
could perceive the least trace of the reflected tints. 
I have repeated the experiment with every precau- 
tion, and with every variation that I could think of, 
and I consider it as an established fact, that in such 
coloured bodies the complementary reflected colour 
cannot be rendered visible. If the fluid, for example, 
be red, the green light from which the red has been 
separated ought to appear either directly by looking 
into the coloured mass, or ought to be recognised 
by its influence in modifying the light really re- 
flected; but as it cannot be seen, we must conclude 
that it has not been reflected, but has been de- 
stroyed by some other property of the coloured 
body. 

A similar objection may be drawn from the disap- 
pearance of the transmitted complementary colour 
in the leaves of plants and petals of flowers. I have 
ascertained from numerous experiments, that the 
transmitted colour is almost invariably the same 
with the reflected colour, and that the same holds 
true with the coloured juices expressed from them. 
The complementary tints are never seen, and wher- 
ever there has been any thing like an approximation 
to two tints, I have invariably found that it arose 
from there being two different coloured juices exist- 
ing hi different sides of the leaf. 

In the phenomena of the light transmitted by 
coloured glasses, there are some peculiarities which, 
we think, demonstrate that their colours are not 
those of thin plates. The light, for example, trans- 
mitted through a particular kind of blue glass, has a 
blue colour of such a peculiar composition that there 
is no bine in any of the orders of colours in thii 
plates which has any resemblance to it. It is entirely 



COLOURS OF NATURAL BODIES. 87 

destitute of the red rays which form the middle of 
the red space in the spectrum; so that the particles 
on which the colour depends must reflect the middle 
red rays, and transmit those on each side of it, a 
property which cannot be deduced from the New- 
tonian doctrine. 

The explanation of opacity, as arising from a 
multitude of reflections, is liable to the same ob- 
jection which we have urged against the explana- 
tion of colour. In order to appreciate its weight, 
we must distinguish opacity into two kinds, namely, 
the opacity of whiteness and the opacity of blackness. 
Those bodies which possess the power of reflection 
in the highest degree, such as white metals, chalk, 
and plaster of Paris, never reflect more than one- 
half of the light which falls upon them. The other 
half of the incident light is, according to Newton, 
lost by a multitude of reflections. But how is it 
lost ? Reflection merely changes the direction of the 
particles of light, so that they must again emerge 
from the body, unless they are reflected into fixed 
returning orbits, which detain them for ever in a 
state .of motion within the body. In the case of 
black opacity, such as that of coal, which reflects 
from its first surface only J 7 th of the white light, 
the difficulty is still greater, and we cannot conceive 
how any system of interior reflections could so 
completely stifle f^ths of the whole incident light, 
without some of it returning to the eye in a visible 
form. 

In determining the constitution of bodies that pro- 
duce transparency and blackness, the Newtonian 
theory encounters a difficulty which its author has 
by no means surmounted. Transparency, as we 
have already seen, arises from the "particles and 
their interstices being too small to cause reflections 
in their common surfaces," that is, they must be 
"less than any of those which exhibit colours," or 
"less than is requisite to reflect the white and very 



88 IR ISAAC NEWTON. 

faint blue of the first order. But this is the very same 
constitution which produces blackness by reflection, 
and in order to explain the cause of blackness by 
transmission, or black opacity, Newton is obliged to 
introduce a new principle. 

".For the production of black" says he, "the cor- 
puscles must be less than any of those which ex- 
hibit colours. For at all greater sizes there is too 
much light reflected to constitute this colour. But 
if -they be supposed a little less than is requisite to 
reflect the white and very faint blue of the first or- 
der, they will reflect so very little light as to appear 
intensely black, and yet may perhaps variously refract* 
it to and fro within themselves so long, until it hap- 
pens to be stifled and lost, by which means they will 
appear black in all positions of the eye, without any 
transparency." 

This very remarkable passage exhibits, in a striking 
manner, the perplexity in which our author was in- 
volved by the difficulties of his subject. As the par- 
ticles which produce blackness by reflection are 
necessarily so small as to exclude the existence of 
any reflective forces, he cannot ascribe the loss of 
the intromitted light, as he does in the case of white 
opacity, to " a multitude of reflections ;" and there- 
fore he is compelled to have recourse to refracting 
forces to perform the same office. The reluctance 
with which he avails himself of this expedient is 
well marked in the mode of expression which he 
adopts ; and I am persuaded that when he wrote the 
above passage, he felt the full force of the objec- 
tions to this hypothesis, which cannot fail to pre- 
sent themselves. As the size of the particles which 
produce blackness are intermediate between those 

* In the same paragraph, when speaking of black bodies becoming 
hot, and burning sooner than others, he says that their "effect may pro- 
ceed partly from the multitude of refractions in a little room, and partly 
from the easy commotion of so very small corpuscles." Optics, Part iii. 
Prop. vii. p. 335. 



COLOURS OF NATURAL BODIES. 89 

which produce transparency and those which pro- 
duce colour, approaching closely to the latter, it is 
difficult to conceive why they should refract the in- 
tromitted light, while the greater and smaller par- 
ticles, and even those almost of the same size, should 
be destitute of that property ^ It is, besides, not easy 
to understand how a refraction can take place within 
bodies which shall stifle all the light, and prevent it 
from emerging. Nay, we may admit the existence 
of such refractions, and yet understand how, by a 
compensation in their direction, the refracted rays 
may all emerge from the opaque body. 

The force of these objections is tacitly recognised 
in Pemberton's View of Sir Isaac Newton's Philoso- 
phy ;* and as Newton not only read and approved of 
that work, but even perused a great part of it along 
with its author, we may fairly consider the opinion 
there stated to be his own. 

" For producing black, the particles ought to be 
smaller than for exhibiting any of the colours, viz. 
of a size answering to the thickness of the bubble, 
whereby reflecting little or no light, it appears colour- 
less; but yet they must not be too small, for that will 
make them transparent through deficiency of reflec- 
tions in the inward parts of the body, sufficient to 
stop the light from going through it ; but they must 
be of a size bordering upon that disposed to reflect 
the faint blue of the first order, which affords an 
evident reason why blacks usually partake a little 
of fhat colour." In this passage all idea of refrac- 
tion is abandoned, and that precise degree of size is 
assumed for the particles which leaves a small power 
of reflection, which is deemed sufficient to prevent 
the body from becoming transparent; that is, suffi- 
cient to render it opaque or black. 

The last objection which we shall state to this 
theory is one to which we attach great weight, and, 

* See page 354. 

H2 



t)0 SIR ISAAC NEWTON. 

as it is founded on discoveries and views which have 
been published since the time of Newton, we ven- 
ture to believe, that, had he been aware of them, he 
would never have proposed the theory which we 
are considering. 

When light falls upon a thin film such as AEC, 
fig. 9, p. 80, so as to produce the colours of thin 
plates, it follows, from Sir Isaac Newton's theory 
of fits, that a portion of the light is, as usual, re- 
flected at the first surface AE,* while the light which 
forms the coloured image is that which is reflected 
from the second surface EC, so that all the colours 
of thin plates are diluted with the white light re- 
flected from the first surface. Now, in the modern 
theory, which ascribes the colours of thin plates to 
the interference of the light reflected from the 
second surface EC, with the light reflected from the 
first surface AE, the resulting tint arises from the 
combination of these two pencils, and consequently 
there is no wliite light reflected from the surface 
AE. In like manner, when the thickness of the 
film is such that the two interfering pencils com- 
pletely destroy one another, and produce black, 
there is not a ray of light reflected from the first 
surface. Here, then, we have a criterion for de- 
ciding between the theory of fits and the theory of 
interference ; for if there is no white light reflected 
from the first surface AE, the theory of fits must be 
rejected. In a remarkable phenomenon of black- 
ness arising from minute fibres, which I have had 
occasion to describe, there was no perceptible re- 
flection from the surface of the fibres ;f and M. 
Fresnel describes an experiment made to deter- 
mine the same point, and states the result of it to 

* When Newton speaks of bodies losing their reflecting power from 
their thinness, he means the reflecting power of their second surfaces, 
as is evident from the reason he assigns. See Optics, Part iii. Prop, xiii, 
p. 257. 

\ Edinburgh Journal of Science, No I p. 108. 



COLOURS OF NATURAL BODIES. 91 

have been unequivocally in favour of the doctrine 
of interference. 

In order to apply this important fact, let us take 
a piece of coal, one of the blackest and most opaque 
of all substances, and which does not reflect to the 
eye a single ray out of those which enter its sub- 
stance. The size of its particles is so small, that 
they are incapable of reflecting light. When a num- 
ber of these particles are placed together, so as to 
form a surface, and other particles behind them, so 
as to form a solid, they will not acquire by this 
process the power of reflection ; and consequently, a 
piece of coal so composed should be destitute of the 
property of reflecting light from its first surface. 
But this is not the case, light is abundantly re- 
flected from the first surface of the coal, and conse- 
quently, its elementary particles must possess the 
same power. Hence the blackness of coal must be 
ascribed to some other cause than to the minute- 
ness of its transparent atoms. 

To transparent bodies this argument has a similar 
application. As their atoms are still less than those 
of black bodies, their inability to reflect light is still 
greater, and hence arises their transparency. But 
the particles forming the surface of such bodies do 
reflect light, and, therefore, their transparency must 
have another origin. 

In the case of coloured bodies, too, the particles 
forming their surfaces reflect white light like those 
of all other bodies, so that these particles cannot 
produce colour on the same principles as those of 
thin plates. In many of those cases of colour which 
seem to depend upon the minuteness of the particles 
of the body, the reflection of white light may never- 
theless be observed, but this will be found to arise 
from a thin transparent film, behind which the colo- 
rific particles are placed. 

Whatever answer may be given to these objec- 
tions, we think it will be admitted by those who 



92 SIR ISAAC NEWTON. 

have studied the subject most profoundly, that a 
satisfactory theory of the colours of natural bodies 
is still a desideratum in science. How far we may 
be able to approach to it in the present state of 
optics the reader will judge from the following 
views. 

Colours may be arranged into seven classes, each 
of which depends upon different principles. 

1. Transparent coloured fluids transparent col 
cured gems transparent coloured glasses coloured 
powders and the colours of the leaves and flowers 
of plants. 

2. Oxidations on metals colours of Labrador 
feldspar colours of precious and hydrophanous 
opal, and other opalescences the colours of the 
feathers of birds, of the wings of insects, and of the 
scales of fishes. 

3. Superficial colours, as those of mother-of-pearl 
and striated surfaces. 

4. Opalescences and colours in composite crystals 
having double refraction. 

5. Colours from the absorption of common and 
polarized light by doubly refracting crystals. 

6. Colours at the surfaces of media of different 
dispersive powers. 

7. Colours at the surface of media in which the 
reflecting forces extend to different distances, or fol- 
low different laws. 

The first two of these classes are the most im- 
portant. The Newtonian theory appears to be 
strictly applicable to the phenomena of the second 
class ; but those of the first class cannot, we con- 
ceive, be referred to the same cause. 

The rays of solar light possess several remarkable 
physical properties : They heat they illuminate 
they promote chymical combination they effect 
chymical decompositions they impart magnetism 
to steel thej alter the colours of bodies thev 



NEW THEORY OF COLOURS. 93 

communicate to plants and flowers their peculiar 
colours, and are in many cases necessary to the 
development of their characteristic qualities. It is 
impossible to admit for a moment that these varied 
effects are produced by a mere mechanical action, 
or that they arise from the agitation of the particles 
of bodies by the vibration of the ether which is con- 
sidered to be the cause of light. Whatever be the 
difficulties which attach to the theory which sup- 
poses light to consist of material particles, we are 
compelled, by its properties, to admit that light acts 
as if it were material, and that it enters into combi- 
nations with bodies, in order to produce the effects 
which we have enumerated. 

When a beam of light falls upon a body, and the 
whole or a part of that which enters its substance 
totally disappears, we are entitled to say, that it is 
detained by some power exercised by the particles 
of the body over the particles of light. When this 
light is said to be lost by a multitude of reflections 
or refractions, the statement is net only hypotheti- 
cal, but it is an hypothesis incompatible with optical 
principles. That the light detained within bodies 
has been stopped by the attractive force of the par- 
ticles seems to be highly probable, and the mind 
will not feel any repugnance to admit that the par- 
ticles of all bodies, whether solid, fluid, or aeriform, 
have a specific affinity for the particles of light. 
Considering light, therefore, as material, it is not 
difficult to comprehend how it should, like other 
elementary substances, enter into combination with 
bodies, and produce many chymical and physical 
effects, but particularly the phenomena of transpa- 
rency, opacity, and colour. 

In transparent colourless bodies, such as water 
and glass, the intromitted light experiences a con- 
siderable loss, because a certain number of its par- 
ticles are attracted and detained by the atoms of the 
water or glass, and the light which emerges is 



94 SIR ISAAC NEWTON. 

colourless, because the particles exercise a propor- 
tional action over all the simple colours which 
compose white light. 

When the transparent body has any decided 
colour, such as those enumerated in Class L, then 
the particles of the- body have exercised a specific 
attraction over those rays of white light which are 
complementary to those which compose the colour 
of the transmitted light. If the transparent body, 
for example, is red, then its particles have detained 
the green rays which entered into the incident light, 
or certain other rays, which with the red are neces- 
sary to compose white light. In compound bodies, 
like some of the artificial glasses, the particles will 
attract and detain rays of light of different colours, 
as may be seen by analyzing the transmitted light 
with a prism, which will exhibit a spectrum deprived 
of all the rays which have been detained. In black 
bodies the particles exercise a powerful attraction 
over light, and detain all the intromitted rays. 

When coloured bodies are opaque, so as to ex- 
hibit their colours principally by reflection, the light 
which is reflected back to the observer has received 
its colour from transmission through part of the 
thickness of the body, or, what is the same thing, 
the colour reflected to the eye is complementary to 
that which has been detained by the particles of the 
body while the light is passing and repassing 
through a thickness terminated by the reflecting 
surfaces ; and as only a part of this light is reflected, 
as in the case of leaves and flowers, the transmitted 
light must have the same colour as the reflected 
light. 

When coloured bodies exhibit two different colours 
complementary to each other, the one seen by re- 
flection and the other by transmission, it is then 
highly probable that the colours are those of thin 
plates, though there are still other optical principles 
to which they may be referred. As the particles of 



NEW THEORY OF COLOURS. 95 

| bodies, and the medium which unites them, or. as 
the different atoms of a compound body may have 
different dispersive powers, while they exercise the 
same refractive force over a particular part of the 
spectrum, the rays for which this compensation 
takes place will be transmitted, while part of the 
complementary light is reflected.* Or in cases 
where the refractive and dispersive powers are the 
same, the reflective forces of the particles may vary 
according to a different law, so that at the separat- 
ing surfaces either white or coloured light may be 
reflected.f 

In those cases of colour where the reflected and 
the transmitted tints are not complementary, as in 
leaf-gold, where the former is yellow and the latter 
green; in leaf -silver, where they are white and blue, 
and in certahTpieees of fir-wood, where the reflected 
light is whitish yellow, and the transmitted light a 
brilliant homogeneous red, we may explain the sepa- 
ration of the colours either by the principles we 
have already laid down or by the doctrine of 'thin 
plates. On the first principle, the colour of the re- 
flected light, which is supposed to be the same as 
that of the transmitted light, will be modified by the 
law according to which the particles of the body 
attract different rays out of the beam of white light. 
In pitch, for example, the blue rays are first ab- 
sorbed, so that at small thicknesses the transmitted 
light is a fine yellow, while, by the action of a 
greater thickness, the yellow itself is absorbed, and 
the transmitted light is a bright homogeneous red. 
Now in leaf-gold the transmitted colour of thinner 
films than we can obtain may be yellow, and, con- 
sequently, the light reflected from the first strata of 
interrupting faces will be yellow, and will determine 
the predominant tint of the reflected light. On the 
Newtonian doctrine, Mr. Herschel has explained it 

* See the Phil. Trans. 1829, Part I. p. 189. 



96 



SIR ISAAC NEWTON. 



by saying", " that the transmitted rays have traversed 
the whole thickness of the medium, and therefore 
undergo many more times the action of its atoms 
than those reflected, especially those near the first 
surface to which the brighter part of the reflected 
colour is due." 

The phenomena of the absorption of common 
and polarized light, which I have described in an- 
other place,* throw much light on the subject of 
coloured bodies. The relation of the absorbent ac 
tion to the axes of double refraction, and, conse- 
quently, to the poles of the molecules of the crystal, 
shows how the particles of light attracted by the 
molecules of the body will vary, both in their nature 
and number, according to the direction in which 
they approach the molecules ; and explains how the 
colour of a body may be changed, either tempora- 
rily or permanently, by heat, according as it pro- 
duces a temporary or a permanent change in the 
relative position of the molecules. This is not the 
place to enlarge on this subject ; but we may be 
permitted to apply the idea to the curious experi- 
ment of Thenard on phosphorus. When this sub- 
stance is rendered pure by repeated distillation, it 
is transparent, and transmits yellow light ; but when 
it is thrown in a melted state into cold water, it 
becomes jet black. When again melted, it resumes 
its original colour and transparency. According to 
the Newtonian theory, we must suppose that the 
atoms of the phosphorus have been diminished in 
size by sudden cooling, an effect which it is not 
easy to comprehend; but, according to the pre- 
ceding views, we may suppose that the atoms of 
the phosphorus have been forced by sudden cooling 
into relative positions quite different from those 
which they take when they slowly assume the solid 
state, and their poles of maximum attraction, in 

* Phil. Trans. 1819, p. 11. 



NEW THEORY OF COLOURS. 9? 

place of being turned to one another, are turned in 
{different directions, and then allowed to exercise 
their full action in attracting the intromitted light, 
and detaining it wholly within the body.* 

Before concluding this chapter, there is one topic 
peculiarly deserving our notice, namely, the change 
of colour produced in bodies by continued exposure 
to light. The general effect of light is to diminish 
or dilute the colours of bodies, and in many cases 
to deprive them entirely of their colour. Now, it 
is not easy to understand how repeated undulations 
propagated through a body could diminish the size 
of its particles, or how the same effect could be 
produced by a multitude of reflections from particle 
to particle. But if light is attracted by the particles 
of bodies, and combines with them, it is easy to 
conceive that, when the molecules of a body have 
combined with a great number of particles of a 
green colour, for example, their power of combina- 
tion with others will be diminished, and, conse- 
quently, the number of particles of any colour 
(absorbed or detained must diminish with the time 
that the body has been exposed to light ; that is, 
[these particles must enter into the transmitted and 
((reflected pencils, and diminish the intensity of their 
colour. If the body, for example, absorbs red light, 
and transmits and reflects green, then if the quan- 
tity of absorbed red light is diminished, it will enter 
into the reflected and transmitted pencils, and, form- 
ing white light by its mixture with a portion of the 
green rays, will actually dilute them in the same 
manner as if a portion of white light had been 
added.f 

* If this view of the matter be just, we should expect that the specific 
gravity of the black would exceed that of the yellow phosphorus. 

t Since the two preceding chapters were written, I have had occasion 
to confirm and extend the views which they contain by many new ex- 
periments. 



08 SIR ISAAC NEWTON. 



CHAPTER VIII. 

Newton's Discoveries respecting the Inflection or Diffraction of Light 
Previous Discoveries of Grimaldi and Dr. Hooke Labours of sue* 
ceeding Philosophers Law of Interference of Dr. Young FresneVt 
Discoveries New Theory of Inflection on the Hypothesis of the Ma- 
teriality of Light. 



ALTHOUGH the discoveries of Newton respectin^ 
the Inflection of Light were first published in hisl 
Optics in 1704, yet there is reason to think that 
they were made at a much earlier period. Sir Isaac,; 
indeed, informs us, in his preface to that great worfy 
that the third book, which contains these discove- 
ries, " was put together out of scattered papers ;'* 
and he adds at the end of his observations, that " he 
designed to repeat most of them with more care and 
exactness, and to make some new ones for determin- 
ing the manner how the rays of light are bent in their 
passage by bodies, for making the fringes of colours 
with the dark lines between them. But I was then 
interrupted, and cannot now think of taking these 
things into consideration." On the 18th March, 1674, 
Dr. Hooke had read a valuable memoir on the phe- 
nomena of diffraction ; and, as Sir Isaac makes no 
allusion whatever to this work, it is the more proba- 
ble that his " scattered papers" had been written 
previous to the communication of Dr. Hooke's ex- 
periments. 

The phenomena of the inflection of light were first 
discovered by Francis Maria Grimaldi, a learned 
Jesuit, who has described them in a posthumous 
work published in 1665, two years after his death.* 

Having admitted a be am of the sun's light through 

* Pkysieo-Mathesis de Lumine coloribus et iride aliisyue^annexit, 
Bonon 1666. 



INFLECTION OF LIGHT. 3$ 

a small pin-hole in a piece of lead or card into a 
dark chamber, he found that the light diverged from 
this aperture in the form of a cone, and that the 
shadows of all bodies placed in this light were not 
only larger than might have been expected, but were 
surrounded with three coloured fringes, the nearest 
the widest, and the most remote the narrowest. 
[n strong light he discovered analogous fringes 
within the shadows of bodies, which increased in 
number with the breadth of the body, and became 
more distinct when the shadow was received obliquely 
and at a greater distance. When two small aper- 
;ures or pin-holes were placed so near each other 
that the cones of light formed by each of them 
ntersected one another, Grimaldi observed, that a 
spot common to the circumference of each, or, which 
s the same thing, illuminated by rays from each 
eone, was darker than the same spot when illumi- 
nated by either of the cones separately ; and he an- 
nounces this remarkable fact in the following para- 
doxical proposition, " that a body actually illuminated^ 
may become more dark by adding a light to that which \ 
t already receives" 

Without knowing what had been done by the 
kalian philosopher, our countryman, Dr. Robert 
looke, had been diligently occupied with the same 
subject. In 47&. he communicated his first obser- 
vations to the Royal Society, and he then spoke of 
lis paper as " containing the discovery of a new 
>roperty of light not mentioned by any optical wri- 
;ers before him." In his paper of 1674, already 
mentioned, and which is no doubt the one to~ which 
he alludes, he has not only described the leading 
phenomena of the inflection, or the deflection of 
light, as he calls it, but he has. distinctly announced 
the doctrine of interference, which has performed so 
great a part in the subsequent history of optics.* 

This doctrme is thus announced. 1. That the same rays of light 
upon the same point of an object will turn into all sorts of colour* 



100 



SIR ISAAC NEWTON. 



Such was- the state of the subject when Newton 
directed to it his powers of acute and accurate ob- 
servation. His attention was turned only to the 
enlargement of the shadow, and to the three fringes 
which surrounded it ; and he begins his observations 
by ascribing the discovery of these facts to Gri- 
maldi. After taking exact measures of the diameter 
of the shadow of a human hair, and of the breadth 
of the fringes at different distances behind it, he 
discovered the remarkable fact that these diame- 
ters and breadths were not proportional to the dis- 
tances from the hair at which they were measured. 
In order to explain these phenomena, Newton sup- 
posed that the rays which passed by the edge of the 
hair are deflected or turned aside from it, as if by a 
repulsive force, the nearest rays suffering the great- 
est, and those more remote a less degree of deflec- 
tion. 

Fig. 10. 




by the various inclination of the object. 2. That colours begin to appear 
when two pulses of light are blended so well and so near together that 
the sense takes them for one. 



INFLECTION OF LIGHT. tfl 

Thus, if X, fig. 10, represents a section of the 
hair, and AB, CD, EF, GH, &c. rays passing at dif- 
ferent distances from X, the ray AB will be more 
deflected than CD, and will cross it at m, the ray 
CD will for the same reason cross EF at n, and 
EF will cross GH at o. Hence the curve or caustic 
formed by the intersections m, n, o, &c. will be con- 
vex outward, its curvature diminishing as it recedes 
from the vertex. As none of the passing light can 
possibly enter within this curve, it will form the 
boundary of the shadow of X. 

The explanation given by Sir Isaac of the coloured 
fringes is less precise, and can be inferred only from 
the two following queries. 

1. "Do not the rays which differ in refrangibility 
differ also in flexibility, and are they not, by these 
different inflections separated from one another, so 
as after separation to make the colours in the three 
fringes above described 1 And after what manner 
are they inflected to make those fringes 1 

2. " Are not *the rays of light in passing by the 
edges and sides of bodies bent several times back- 
wards and forwards with a motion like that of an 
eel ? And do not the three fringes of light above 
mentioned arise from three such bendings ?" 

The idea thus indistinctly thrown out in the pre- 
ceding queries has been ingeniously interpreted by 
Mr. Herschel in the manner represented in fig. 11, 
where SS are two rays passing by the edge of the 
body MN. These rays are supposed to undergo 
several bendings, as at a, b, c, and the particles of 
light are thrown off at one or other of the points 
of contrary flexure, according to the state of their 
fits or other circumstances. Those that are thrown 
outwards in the direction A, &B, cC, dD, will 
produce as many caustics by their intersections as 
there are deflected rays; and each caustic, when re- 
ceived on a screen at a distance, will depict on it 
the brightest part or maximum of a fringe. 
12 



102 SIR ISAAC NEWTON. 

Fig. 11. S S 




In this unsatisfactory state was the subject of the 
inflection of light left by Sir Isaac. His inquiries 
were interrupted, and never again renewed; and 
though he himself found that the phenomena were 
the same, " whether the hair was encompassed with 
air or with any other pellucid substance," yet this 
important result does not seem to have shaken his 
conviction, that the phenomena had their origin in 
the action of bodies upon light. 

During two sets of experiments which I made on 
the inflection of light, the first in 1798, and the 
second in 1812 and 1813, 1 was desirous of examin- 
ing the influence of density and refractive power 
over the fringes produced by inflection. T com- 



DR. YOUNG'S LAW OF INTERFERENCE. 103 

pared the fringes formed by gold-leaf with those 
formed by masses of gold, and those produced by 
films which gave the colours of thin plates with 
those formed by masses of the same substance. I 
examined the influence of platinum, diamond, and 
cork in inflecting light, the effect of non-reflecting 
grooves and spaces in polished metals, and of cylin- 
ders of glass immersed in a mixture of oil of cassia 
and oil of olives of the same refractive power; and, 
as the fringes had the same magnitude and charac- 
ter under all these circumstances, I concluded that 
they were not produced by any force inherent in 
the bodies themselves, but arose from a property 
of the light itself, which always showed itself when 
light was stopped in its progress. 

Dr. Thomas Young, who had supported with great 
ingenuity and force of argument the undulatory 
theory of light, as maintained by Hooke and Huy- 
gens, was the first who gave a plausible explana- 
tion of the inflection of light. By interposing a 
small screen at B, fig. 10, and intercepting the 
rays that passed near the hair X, he was surprised 
to find that all the fringes within the shadow disap- 
peared. The same effect took place when the screen 
intercepted the rays on the other side ; and hence 
he concluded, that the rays on each side of the hair 
were necessary to the production of the inner fringes, 
and that the fringes were produced by the inter" 
ference of the rays that passed on one side of the 
hair with those that passed on the other side. In 
order to account for the coloured fringes without the 
shadow, Dr. Young conceived that the rays which 
pass near the edge of the hair interfere with others, 
which he supposes may be reflected after falling 
very obliquely upon its edge, a supposition which, 
if correct, would certainly produce fringes very 
similar to those actually observed. 

In pursuing these researches so successfully begun 
by Dr. Young, M. Fresnel had the good fortune to 



104 SIR ISAAC NEWTON. 

explain all the phenomena of inflection by means of 
the undulatory doctrine combined with the principle 
of interference. In place of transmitting the light 
through a small aperture, he caused it to diverge 
from the focus of a deep convex lens, and instead 
of receiving the shadow and its fringes upon a 
smooth white surface, as was done by Newton, he 
viewed them directly with his eye through a lens 
placed behind the shadow ; and by means of a mi- 
croscope he was able to measure the dimensions of 
the fringes with the greatest exactness. By this 
mode of observation he made the remarkable dis- 
covery, that the inflection of the light depended on 
the distance of the inflecting body from the aperture or 
from the focus of divergence ;* the fringes being ob- 
served to dilate as the body approached that focus, 
and to contract as it receded from it, their relative 
distances from each other, and from the margin of 
the shadow continuing invariable. In attempting to 
account for the formation of the exterior fringes, M. 
Fresnel found it necessary to reject the supposition 
of Dr. Young, that they were owing to light re- 
flected from the edge of the body. He not only 
ascertained that the real place of the fringe was the 
nnjth of a millimetre different from what it should 
be on that supposition, but he found that the fringes 
preserved the same intensity of light, whether the 
inflecting body had a round or a sharp edge, and 
even when the edge was such as not to afford suffi- 
cient light for their production. From this difficulty 
the undulatory theory speedily released him, and he 
was led by its indications to consider the exterior 
fringes, as produced by an infinite number of ele- 
mentary waves of light emanating from a primitive 
wave when partly interrupted by an opaque body. 
The various phenomena of inflection, which had 

* This effect is so great, that at the distance of four inches from the 
point of divergence, the angular inflexion of the red rays of the first fringe 
is 12' 6", while at the distance of about twenty feet, it is onlv 3' 55" 



NEW THEORY OF INFLECTION. 105 

so long resisted every effort to generalize them, 
having thus received so beautiful and satisfactory an 
explanation from the undulatory doctrine, they must 
of course be regarded as affording to that doctrine 
the most powerful support, while the Newtonian 
hypothesis of the materiality of light is proportion- 
ally thrown into the shade. It is impossible, indeed, 
even for national partiality to consider the views of 
Newton as furnishing any explanation of the facts 
discovered by Fresnel ; and, as no attempt has been 
made by the small though able phalanx of his dis- 
ciples to stay the decision with which, on this count 
at least, the doctrine of emission has been threat- 
ened, we shall venture to suggest some principles 
by which the refractory phenomena may perhaps 
be yet brought within the pale of the Newtonian 
theory. _ 

That the particles of light, like those of heat, ^ 
are endowed with a repulsive force which prevents 
them from accumulating when in a state of conden- 
sation, or when they are detained by the absorptive 
action of opaque bodies, will be readily admitted. 
By this power a beam of light radiating from a 
luminous point has, in every azimuth, the same de- 

I gree of intensity at the same distance from its centre 
of divergence ; but if we intercept a portion of such 

! a beam by an opaque body, the repulsive force of the 
light which formerly occupied its shadow is with- 
drawn, and consequently the rays which pass near 
the body will be repelled into the shadow, and will 
form, by their interference with those similarly re- 
pelled on the other side, the interior fringes, which 
are parallel to the edges of the body. The rays 
which pass at a greater distance will in like manner 
be bent towards the body, but with less force, and, 
interfering with those rays which retain their primi- 
tive direction, from the state of their fits or the 
position of their poles, they will form the exterior 
fringes. When the inflecting body is placed near 



10 SIR ISAAC NEWTON. 

the point of divergence, the greater proximity of 
the rays will produce a greater repulsive force, and 
consequently a greater inflection of the passing 
light ; while the removal of the body from the point 
of divergence will be accompanied with an increased 
distance of the particles, an inferior repulsive force, 
and a feebler inflection. As the phenomena of in- 
flection, considered under this aspect, arise from a 
property of the light itself, it follows that they will 
remain invariable, whatever be the nature or den- 
sity of the body, or the form of the edge which 
acts upon the passing rays. 



CHAPTER IX. 

Miscellaneous Optical Researches of Newton ffis Experiments on 
Refraction His Conjecture respecting the Inflammability of the 
Diamond His Law of Double Refraction His Observations on the 
Polarization of LightNewton's Theory of Light His "Optics* 

BEFORE concluding our account of Newton's op- 
tical discoveries, it is necessary to notice some of 
his minor researches, which, though of inferior im- 
portance in the science of light, have either exer- 
cised an influence over the progress of discovery, 
or been associated with the history of other branches 
of knowledge. 

One of the most curious of these inquiries related 
to the connexion between the refractive powers and 
the chymical composition of bodies. Having meas- 
ured the refractive powers and the densities of twenty- 
two substances, he found that the forces which 
reflect and refract light are very nearly proportional 
to the densities of the same bodies. In^ this law, 
however, he noticed a remarkable exception in the 
case of unctuous and sulphureous bodies, such as 
camphire, olive oil, linseed oil, spirit of turpentine, 



DOUBLE REFRACTION OF LIGHT. 107 

and diamond, which have their refractive powers 
two or three times greater in respect of their densi- 
ties than the other substances in the table, while 
among themselves their refractive powers are pro- 
portional to their densities, without any considerable 
variation. Hence he concluded that diamond " is 
an unctuous substance coagulated," a sagacious 
prediction, which has been verified in the discoveries 
of modern chymistry. The connexion between a 
high degree of inflammability and a great refracting 
force has been still more strongly established by the 
high refractive power which I detected in phospho- 
rus, and which was discovered in hydrogen by MM. 
Biot and Arago. 

There is no part of the optical labours of Newton 
which is less satisfactory than that which relates to 
the double refraction of light. In 1690, Huygens, 
published his admirable treatise on light, in which 
he has given the law of double refraction in calca- 
reous spar, as deduced from his theory of light, and 
as confirmed by direct experiment. Viewing it 
probably as a theoretical deduction, Newton seems 
to have regarded it as incorrect, and though he has 
given Huygens the credit of describing the phe- 
nomena more exactly than Bartholinus, yet, without 
assigning any reason, he rejected the law of the 
Dutch philosopher, and substituted another in its 
place. These observations of our author form the 
subject of the twenty-fifth and twenty-sixth queries at 
the end of his Optics, which was published fourteen 
years after the appearance of Huygens's work. The 
law adopted by Newton is not accompanied with any 
of the experiments from which it was deduced ; and 
though he has given it without expressing any doubt 
of its accuracy, it is, nevertheless, entirely incom- 
patible with observation, and has been rejected by 
all succeeding philosophers. 

In his speculations respecting the successive dis- 
appearance and reappearance of two of the four 



108 SIR ISAAC NEWTON. 

images which are formed when a luminous objecl 
is viewed through two rhombs of calcareous spar, 
one of which is made to revolve upon the other. 
Newton has been more successful. He concluded 
from these phenomena that every ray of light has 
two opposite sides originally endued with the prop- 
erty on which the unusual refraction depends, and 
other two opposite sides not endued with that prop- 
erty; and he suggested it as a subject for future 
inquiry, whether there are not more properties of 
light by which the sides of the rays differ, and are 
distinguished from one another. This is the first 
occasion on which the idea of a polarity in the rays 
of light has been suggested.* 

From the various optical inquiries in which New- 
ton was engaged, he was strongly impressed with 
the belief that light consists of small material par- 
ticles emitted from shining substances, and that 
these particles could be again recombined into solid 
matter, so that " gross bodies and light were con- 
vertible into one another." He conceived also that 
the particles of solid bodies and of light exerted a 
mutual action upon each other, the former being 
agitated and heated by the latter, and the latter 
being attracted and repelled by the former,* with 
forces depending on the inertia of the luminous par- 
ticles. These forces he regarded as insensible at 
all measurable distances, and he conceived that the 
distances between the particles of bodies were very 
small when compared with the extent of their sphere 
of attraction and repulsion. 

With the exception of Hooke, Huygens, and 
Euler, almost all the contemporaries and successors 
of Newton maintained the doctrine of the mate- 
riality of light. It was first successfully assailed by 
Dr. Thomas Young, and since that time it has been 
shaken to its foundation by those great discoveries 

': 

* See the twenty-ninth query at the end of his Optics, where the sides 
of a ray are compared with the poles of a magnet. 



OPTICS. 109 

which have illustrated the commencement of the 
present century. The undulatory theory, which has 
thus triumphed in its turn, is still subject to grave 
difficulties, and we fear another century must elapse 
before a final decision can be pronounced on this 
Jong-agitated question. 

The most important of the optical discoveries of 
Newton, of which we have given a general history, 
were communicated to the Royal Society in de- 
tached papers ; but the disputes in which they had 
involved their author made him hesitate about the 
publication of his other discoveries. Although he 
had drawn up a connected view of his labours under 
the title of " Opticks, or a Treatise on the Reflex- 
ions, Refractions, Inflexions, and Colours of Light," 
yet he resolved not to publish this work during the 
life of Hooke, by whose rival jealousy his tranquillity 
had been so frequently interrupted. Hooke, how- 
ever, died in 1702, and the Optics of Newton ap- 
peared in English in 1704. Dr. Samuel Clark pro- 
posed a Latin edition of it, which appeared in 1706, 
and he was generously presented by Sir Isaac with 
500/. (or 100/. for each of his five children), as a 
token of the approbation and gratitude of the author. 
Both the English and the Latin editions have been 
frequently reprinted both in England and on the 
Continent,* and there perhaps never was a work of 
profound science so widely circulated 

* Tfce English edition was reprinted at London in 1714, 1721, and 
1730, and the Latin one at London in 1706, 1719, 1721, 1728, at Lausanne 
in 1740, aud at Padua in 1773. 



110 SIR ISAAC NEWTON. 



CHAPTER X. 

Astronomical Discoveries of Newton Necessity of combined Exertion 
to the Completion of great Discoveries Sketch of the History of As- 
tronomy previous to the Time of Newton Copernicus, 1473-1543 
Tycho Brake, 1546-1601 Kepler, 1571-1631 Galileo, 1564-1642. 

FROM the optical labours of Newton we now pro- 
ceed to the history of his astronomical discoveries 
those transcendent deductions of human reason 
by which he has secured to himself an immortal 
name, and vindicated the intellectual dignity of his 
species. Pre-eminent as his triumphs have been, it 
would be unjust to affirm that they were achieved 
by his single arm. The torch of many a preceding 
age had thrown its light into the strongholds of 
the material universe, and the grasp of many a pow- 
erful hand had pulled down the most impregnable of 
its defences. An alliance, indeed, of many kindred 
spirits had been long struggling in this great cause, 
and Newton was but the leader of their mighty 
phalanx, the director of their combined genius, 
the general who won the victory, and therefore 
wears its laurels. 

The history of science presents us with no ex- 
ample of an individual mind throwing itself far in 
advance of its contemporaries. It is only in the 
career of crime and ambition that reckless man 
takes the start of his species, and, uncurbed by 
moral and religious restraint, erects an unholy dy- 
nasty upon the ruins of ancient and venerable insti- 
tutions. The achievements of intellectual power, 
though often begun by one mind and completed by 
another, have ever been the results of combined ex- 
ertions. Slow in their growth, they gradually ap- 
proximate to a more perfect condition : the variety 



ASTRONOMICAL DISCOVERIES. Ill 

i the phenomena of nature call forth a variety of 
intellectual gifts ; the powers of analysis and com- 
bination are applied to the humbler labours of obser 
vation and experiment, and in the ordeal of rival 
inquiry truth is finally purified from error. How 
different is it with those systems which the imagi- 
nation rears, those theories of wild import which 
are directed against the consciences and hopes of 
man. The fatal upas-tree distils its poison in the 
spring as well as the autumn of its growth, but the 
fruit which sustains life must have its bud prepared 
before the approach of winter, its blossom expanded 
in the spring, and its juices elaborated by the light 
and heat of the summer and the autumnal sun. 

In the century which preceded the birth of New- 
ton the science of astronomy advanced with the 
most rapid steps. Emerging from the darkness of 
the middle ages, the human mind seemed to rejoice 
in its new-born strength, and to apply itself with 
elastic vigour to unfold the mechanism of the heavens. 
The labours of Hipparchus and Ptolemy had indeed 
furnished many important epochs and supplied many 
valuable data ; but the cumbrous appendages of 
cycles and epicycles with which they explained the 
stations and retrogradations of the planets, and the 
vulgar prejudices which a false interpretation of 
Scripture had excited against a belief in the motion 
of the earth, rendered it difficult even for great 
minds to escape from the trammels of authority, 
and appeal to the simplicity of nature. 

The sovereign of Castile, the generous and noble- 
minded Alphonso, had long before proscribed the 
rude expedients of his predecessors ; and when he 
declared that if the heavens were thus constituted, 
he could have given the Deity good advice, he must 
not only have felt the absurdity of the prevailing 
system, but must have obtained some foresight of a 
more simple arrangement. But neither he nor the 
astronomers whom he so liberally protected seem to 



112 SIR ISAAC NEWTON. 

have established a better system, and it was left 
to Copernicus to enjoy the dignity of being the 
restorer of astronomy. 

This great man, a native of Thorn in Prussia, fol- 
lowing his father's profession, began his career as a 
doctor of medicine, but an accidental attendance on 
the mathematical lectures of Brudzevius excited a 
love for astronomy, which became the leading pas- 
sion of his life. Quitting a profession uncongenial 
to such pursuits, he went to Bologna to study 
astronomy under Dominic Maria ; and after having 
enjoyed the friendship and instruction of that able 
philosopher, he established himself at Rome in the 
humble situation of a teacher of mathematics. Here 
he made numerous astronomical observations which 
served him as the basis of future researches ; but 
an event soon occurred which, though it interrupted 
for a while his important studies, placed him in a 
situation for pursuing them with new zeal. The 
death of one of the canons enabled his uncle, who 
was Bishop of Ermeland, to appoint him to a can- 
onry in the chapter of Frauenburg, where, in a 
house situated on the brow of a mountain, he con- 
tinued, in peaceful seclusion, to carry on his astro- 
nomical observations. During his residence at Rome 
his talents had been so well appreciated, that the 
Bishop of Fossombrona, who presided over the 
council for reforming the calendar, solicited the aid 
of Copernicus in this desirable undertaking. At first 
he entered warmly into the views of the council, 
and charged himself with the determination of the 
length of the year and of the month, and of the 
other motions of the sun and moon that seemed to 
be required ; but he found the task too irksome, and 
probably felt that it would interfere with those 
interesting discoveries which had already begun to 
dawn upon his mind. 

Copernicus is said to have commenced his inqui- 
ries by an historical examination of the opinions of 



COPERNICUS. 13 

ancient authors on the system of the universe ; buf 
it is more likely that he sought for the authority of 
I their great names to countenance liis peculiar views, 
and that he was more desirous to present his own 
theory as one that he had received, rather than as 
one which he had invented. His mind had been 
long imbued with the idea that simplicity and har- 
mony should characterize the arrangements of the 
planetary system, and, in the complication and dis- 
order which reigned in the hypothesis of Ptolemy, 
he saw insuperable objections to its being regarded 
as a representation of nature. In the opinions of 
the Egyptian sages, in those of Pythagoras, Philo- 
laus, Aristarchus, and Nicetas, he recognised his 
own earliest conviction that the earth was not the 
centre of the universe ; but he appears to have con- 
sidered it as still possible that our globe might per- 
form some function in the system more important 
than that of the other planets; and his attention 
was much occupied with the speculation of Martia- 
nus Capella, who placed the sun between Mars and 
the moon, and made Mercury and Venus revolve 
round him as a centre; and with the system of 
Apollonius Pergaeus, who made all the planets re- 
volve round the sun, while the sun and moon were 
carried round the earth in the centre of the universe. 
The examination, however, of these hypotheses 
gradually dispelled the difficulties with which the 
subject was beset ; and after the labours of more 
than thirty years, he was permitted to see the true 
system of the heavens. The sun he considered as 
immoveable in the centre of the system, while the 
earth revolved between the orbits of Venus and 
Mars, and produced by its rotation about its axis all 
the diurnal phenomena of the celestial sphere. The 
precession of the equinoxes was thus referred to a 
slight motion of the earth's axis, and the stations 
and retrogradations of the planets were the neces- 
sary consequence of their own motions combined 
K2 



114 SIR ISAAC NEWTON. 

with that of the earth about the sun. These re- 
markable views were supported by numerous as- 
tronomical observations; and in 1530 Copernicus 
brought to a close his immortal work on the Revolu- 
tions of the Heavenly Bodies. 

But while we admire the genius which triumphed 
over so many difficulties, we cannot fail to commend 
the extraordinary prudence with which he ushered 
his new system into the world. Aware of the preju- 
dices, and' even of the hostility with which such a 
system would be received, he resolved neither to 
startle the one nor provoke the other. He allowed 
his opinions to circulate in the slow current of per- 
sonal communication. The points of opposition 
which they presented to established doctrines were 
gradually worn down, and they insinuated them- 
selves into reception among the ecclesiastical circles 
by the very reluctance of their author to bring them 
into notice. In the year 1534, Cardinal Schonberg, 
Bishop of Capua, and Gyse, Bishop of Culm, exerted 
all their influence to induce Copernicus to lay his 
system before the world ; but he resisted their so- 
licitations ; and it was not till 1539 that an accidental 
circumstance contributed to alter his resolution. 
George Rheticus, professor of mathematics at Wir- 
temberg, having heard of the labours of Copernicus, 
resigned his chair, and repaired to Frauenberg to 
make himself master of his discoveries. This zeal- 
ous disciple prevailed upon his master to permit the 
publication of his system ; and they seem to have 
arranged a plan for giving it to the world without 
alarming the vigilance of the church, or startling 
the prejudices of individuals. Under the disguise 
of a student of mathematics, Rheticus published in 
1540 an account of the manuscript volume of Coper- 
nicus. This pamphlet was received without any 
disapprobation, and its author was encouraged to 
reprint it at Basle, in 1541, with his own name. 
The success of these publications, and the flattering 



TYCHO BRAKE. 115 

manner in which the new astronomy was received 
by several able writers, induced Copernicus to place 
his MSSj in the hands of Rheticus. It was accord- 
ingly printed at the expense of Cardinal Schon- 
berg, and appeared at Nuremberg in 1543. Its illus- 
trious author, however, did not live to peruse it. 
A complete copy was handed to him in his last 
moments, and he saw and touched it a few hours 
before his death. This great work was dedicated 
to the Holy Pontiff, in order, as Copernicus himself 
says, that the authority of the head of the church 
might silence the calumnies of individuals who had 
attacked his views by arguments drawn from reli- 
gion. Thus introduced, the Copernican system met 
with no ecclesiastical opposition, and gradually made 
its way in spite of the ignorance and prejudices 
of the age. 

Among the astronomers who provided the mate- 
rials of the Newtonian philosophy the name of 
Tycho Brahe merits a conspicuous place. De- 
scended from an ancient Swedish family, he was 
born at Knudstorp, in Norway, in 1546, three years 
after the death of Copernicus. The great eclipse 
of the sun which happened on the 26th August, 
1560, while he was at the University of Copenhagen, 
attracted his notice : and when he found that all 
its phenomena had been accurately predicted, he 
was seized with the most irresistible passion to ac- 
quire the knowledge of a science so infallible in its 
results. Destined for the profession of the law, his 
friends discouraged the pursuit which now engrossed 
his thoughts; and such were the reproaches and 
even persecutions to which he was exposed, that he 
quitted his country with the design of travelling 
through Germany. At the very commencement of 
his journey, however, an event occurred in which 
the impetuosity of his temper had nearly cost him 
his life. At a wedding-feast in Rostock, a question- 
able point in geometry involved him in a dispute 



116 SIR ISAAC NEWTON. 

with a Banish nobleman of the same temperament 
with himself ; and the two mathematicians B^solved 
to settle the difference by the sword. /Tycjio, 
however, seems to have been second in the conflict, 
for he lost the greater part of his nose, and was 
obliged to supply its place by a substitute of gold 
and silver, which a cement of glue attached to his 
face. ^During his stay at Augsburg lie inspired the 
burgomaster of the city, Peter Hainzell, with a love 
of astronomy. This public-spirited citizen erected 
an excellent observatory at his own expense, and 
here Tycho began that distinguished career which 
has placed him in the first rank of practical as- 
tronomers. 

Upon his return to Copenhagen in 1570, he was 
received with every mark of respect. The king in- 
vited him to court, and persons of all ranks harassed 
him with their attentions. At Herritzvold, near his 
native place, the house of his maternal uncle afforded 
him a retreat from the gayeties of the capital, and 
he was there offered every accommodation for the 
prosecution of his astronomical studies. Here, 
however, the passion of love and the pursuits of 
alchymy distracted his thoughts ; but though the 
peasant girl of whom he was enamoured was of 
easier attainment than the philosopher's stone, the 
marriage produced an open quarrel with his relations, 
which it required the interference of the king to allay. 
In the tranquillity of domestic happiness, Tycho re- 
sumed his study of the heavens, and in 1572 he 
enjoyed the singular good fortune of observing, 
through all its variations, the new star in Cassiopeia, 
which appeared with such extraordinary splendour 
as to be visible in the daytime, and which gradually 
disappeared in the following year. 

Dissatisfied with his residence in Denmark, Tycho 
resolved to settle in some distant country ; and hav- 
ing gone as far as Venice in search of a suitable 
residence, he at last fixed upon Basle, in Switzer* 



TYCHO BRAKE. 117 

land. The King of Denmark, however, had learned 
his intention from the Prince of Hesse ; and when 
Tycho returned to Copenhagen to remove his family 
and his instruments, his sovereign announced to him 
his resolution to detain him in his kingdom. He 
presented him with j the canonry of Roschild, with 
an income of 2000 crowns per annum. To this he 
added a pension of 1000 crowns ; and he promised 
to give him the island of Huen, with a complete 
observatory erected under his own eye. This gene- 
rous offer was instantly accepted. The celebrated 
observatory of Uraniburg was established at the 
expense of about 20,000/. ; and in this magnificent 
retreat Tycho continued for twenty-one years to en- 
rich astronomy with the most valuable observations. 
Admiring disciples crowded to this sanctuary of the 
sciences to acquire the knowledge of the heavens ; 
and kings* and princes felt themselves honoured 
by becoming the guests of the great astronomer of 
the age. 

One of the principal discoveries of Tycho was 
that of the inequality of the moon's motion, called 
the variation. He detected, also, the annual equa- 
tion which affects the place of her apogee and nodes, 
and he determined the greatest and the least inclina- 
tion of the lunar orbit. His observations on the 
planets were numerous and precise, and have formed 
the data of the present generalizations in astronomy. 

* When James I. went to Copenhagen in 1590, to'conclude his mar- 
riage with the Princess Anne of Denmark, he spent eight days under 
the roof of Tycho at Uranihurg. As a token of his gratitude, he com- 
posed a set of Latin verses in honour of the astronomer, and left him a 
magnificent present at his departure. He gave him also his royal license 
for the publication of his works in England, and accompanied it with 
the following complimentary letter : 

" Nor am I acquainted with these things on the relation of others, or 
from a mere perusal of your works, but I have seen them with my own 
eyes, and heard them with my own ears, in your residence at Urani 
burg, during the various learned and agreeable conversations which I 
there held with you, which even now affect my mind to such a degree, 
that it is difficult to decide whether I recollect them with greater pleasure 
or admiration." 



118 SIR ISAAC NEWTON. 

Though thus skilful in the observation of phenomena, 
his mind was but little suited to investigate their 
cause, and it was probably owing to this defect that 
he rejected the system of Copernicus. The vanity 
of giving his own name to another system was not 
likely to actuate a mind such as his, and it was more 
probable that he was led to adopt the immobility of 
the earth, and to make the sun, with all his attendant 
planets, circulate round it, from the great difficulty 
which still presented itself by comparing the apparent 
diameter of the stars with the annual parallax of the 
earth's orbit. 

The death of Frederick in 1588 proved a severe 
calamity to Tycho, and to the science which he cul- 
tivated. During the first years of the minority of 
Christian IV. the regency continued the royal patron- 
age to the observatory of Uraniburg; and in 1592 
the young king paid a visit of some days to Tycho, 
and left him a gold chain in token of his favour. 
The astronomer, however, had made himself enemies 
at court, and the envy of his high reputation had 
probably added fresh malignity to the irritation of 
personal feelings. Under the ministry of Wolchen- 
dorf, a name for ever odious to science, Tycho's 
pension was stopped ; he was in 1597 deprived of 
the canonry of Roschild, and was thus forced, with 
his wife and children, to seek an asylum in a foreign 
land. His friend, Henry Rantzau, of Wansbeck, 
under whose roof he found a hospitable shelter, was 
fortunately acquainted with the emperor Rodolph II., 
who, to his love of science, added a passion for 
alchymy and astrology. The reputation of Tycho 
having already reached the imperial ear, the recom- 
mendation of Rantzau was scarcely necessaiy to en- 
sure him his warmest friendship. Invited by the em- 
peror, he repaired in 1599 to Prague, where he met 
with the kindest reception. A pension of three 
thousand crowns was immediately settled upon him, 
and a commodious observatory erected for his use 



TYCHO BRAKE. 119 

In the vicinity of that city. Here the exiled astrono- 
mer renewed with delight his interrupted labours, 
and the gratitude which he cherished for the royal 
favour increased the satisfaction which he felt in 
having so unexpectedly found 3. resting-place for 
approaching age. These prospects of better days 
were enhanced by the good fortune of receiving two 
such men as Kepler and Longomontanus for his 
pupils ; but the fallacy of human anticipation was 
here, as in so many other cases, strikingly displayed. 
Tycho was not aware of the inroads which both his 
labours and his disappointments had made upon his 
constitution. Though surrounded with affectionate 
friends and admiring disciples, he was still an exile 
in a foreign land. Though his country had been 
base in its ingratitude, it was yet the land which he 
loved, the scene of his earliest affection, the 
theatre of his scientific glory. These feelings con- 
tinually preyed upon his mind, and his unsettled 
spirit was ever hovering among his native mountains. 
In this condition he was attacked with a disease of 
the most painful kind, and though the paroxysms of 
its agonies had lengthened intermissions, yet he saw 
that death was approaching. He implored his pupils 
to persevere in their scientific labours. He conversed 
with Kepler on some of the profoundest points of 
astronomy, and with these secular occupations he 
mingled frequent acts of piety and devotion. In 
this happy condition he expired without pain at the 
age of fifty-five, the unquestionable victim of the 
councils of Christian IV. 

Notwithstanding the accessions which astronomy 
had received from the labours of Copernicus and 
Tycho, no progress was 'yet made in developing 
the general laws of the system, and scarcely an idea 
had been formed of the power by which the planets 
were retained in their orbits. The labours of as- 
siduous observers had supplied the materials for this 



120 SIR ISAAC NEWTON. 

purpose, and Kepler arose to lay the foundations of 
physical astronomy. 

John Kepler was born at Wiel, in Wirtemberg, in 
1571. He was educated for the church, and dis- 
charged even some of the clerical functions; but his 
devotion to science withdrew him from the study of 
theology. Having received mathematical instruc- 
tion from the celebrated Maestlinus, he had made 
such progress in the science, that he was invited in 
1594 to fill the mathematical chair of Gratz in Sty- 
ria. Endowed with a fertile imagination, his mind 
was ever intent upon subtle and ingenious specula- 
tions. In the year 1596 he published his peculiar 
views in a work on the Harmonies and Analogies of 
Nature. In this singular production, he attempts to 
solve what he calls the great cosmographical mys- 
tery of the admirable proportion of the planetary 
orbits ; and by means of the six regular geometrical 
solids,* he endeavours to assign a reason why there 
are six planets, and why the dimensions of their 
orbits and the time of their periodical revolutions 
were such as Copernicus had found them.. If a 
cube, for example, were inserted in a sphere, of which 
Saturn's orbit was one of the great circles, it would, 
he supposed, touch by its six planes the lesser 
sphere of Jupiter ; and, in like manner, he proposes 
to determine, by the aid of the other geometrical 
solids, the magnitude of the spheres of the other 
planets. A copy of this work was presented by its 
author to Tycho Brahe, who had been too long 
versed in the severe realities of observation to at- 
tach any value to such wild theories. He advised 
his young friend " first to lay a solid foundation for 
his views by actual observation, and then, by ascend- 
ing from these, to strive to reach the causes of 
things ;" and there is reason to think that, by the aid 
of the whole Baconian philosophy, thus compressed 

* The cube, the sphere, the tetrahedron, the octahedron, the dodeca- 
hedron, and the icosahedron. 



KEPLER. 121 

by anticipation into a single sentence, he abandoned 
for a while his visionary inquiries. 

In the year 1598 Kepler suffered persecution for 
his religious principles, and was compelled to quit 
Gratz ; but though he was recalled by the States of 
Styria, he felt his situation insecure, and accepted of 
a pressing invitation from Tycho to settle at Prague, 
and assist him in his calculations. Having arrived 
in Bohemia in 1600, he was introduced by his friends 
to the Emperor Rodplph, from whom he ever after- 
ward received the kindest attention. On the death 
of Tycho in 1601, he was appointed mathematician 
to the emperor, a situation in which he was con- 
tinued during the successive reigns of Matthias and 
Ferdinand; but what was of more importance to 
science, he was put in possession of the valuable 
collection of Tycho's observations. These obser- 
vations were remarkably numerous ; and as the orbit 
of Mars was more oval than that of any of the other 
planets, they were peculiarly suitable for determin- 
ing its real form. The notions of harmony and 
symmetry in the construction of the solar system, 
which had filled the mind of Kepler, necessarily led 
him to believe that the planets revolved with a uni- 
form motion in circular orbits. So firm, indeed, was 
this conviction, that he made numerous attempts to 
represent the observations of Tycho by this hy- 
pothesis. The deviations were too great to be as- 
cribed to errors of observation ; and in trying various 
other curves, he was led to the discovery that Mars 
revolved round the sun in an elliptical orbit, in one 
of the foci of which the sun itself was placed. The 
same observations enabled him to determine the 
dimensions of the planet's orbit, and by comparing 
together the times in which Mars passed over 
different portions of its orbit, he found that they 
were to one another as the areas described by the 
lines drawn from the centre of the planet to the 
centre of the sun, or, in more technical terms, that 
L 



122 SIR ISAAC NEWTON. 

the radius vector describes equal areas in equal 
times. These two remarkable discoveries, the nrst 
that were ever made in physical astronomy, were 
extended to all the other planets of the system, and 
were communicated to the world in 1609, in his 
" Commentaries on the Motions of the Planet Mars, 
as deduced from the observations of Tycho Brahe." 
Although our author was conducted to these great 
laws by the parent examination of well-established 
facts, his imagination was ever hurrying him among 
the wilds of conjecture. Convinced that the mean 
distances of the planets from the sun bore to one 
another some mysterious relation, he not only com- 
pared them with the regular geometrical solids, but 
also with the intervals of musical tones ; an idea 
which the ancient Pythagoreans had suggested, and 
which had been adopted by Archimedes himself. 
All these comparisons were fruitless ; and Kepler 
was about to abandon an inquiry of about seventeen 
years' duration, when, on the 8th March, 1618, he 
conceived the idea of comparing the powers of the 
different members which express the planetary dis- 
tances, in place of the numbers themselves. He 
compared the squares and the cubes of the distances 
with the same powers of the periodic times ; nay, he 
tried even the squares of the times with the cubes 
of the distances ; but his hurry and impatience led 
him into an error of calculation, and he rejected this 
law as having no existence in nature ! On the 15th 
May, his mind again reverted to the same notion, 
and upon making the calculations anew, and free from 
error, he discovered the great law, that the squares 
of the periodic times of any two planets are to one 
another as the cubes of their distances from the sun. 
Enchanted with this unexpected result, he could 
scarcely trust his calculations ; and, to use his own 
language, he at first believed that he was dreaming, 
and had taken for granted the very truth of which 
he was in search. This brilliant discovery was pub- 



KEPLER. 123 

lished in 1619, in his "Harmony of the World';" a 
I work dedicated to James VI. of Scotland. Thus 
! were established what have been called the three 
i laws of Kepler, the motion of the planets in ellip- 
< tical orbits, the proportionality between the areas 
described and their times of description, and the 
relations between the squares of the periodic times 
!' and the cubes of the distances. 

The relation of the movements of the planets to 
the sun, as the general centre of all their orbits, 
could not fail to suggest to Kepler that some power 
resided in that luminary by which these various mo- 
tions were produced ; and he went so far as to con- 
jecture that this power diminishes as the square of 
jj the distance of the body on which it was exerted ; 
i but he immediately rejects this law, and prefers that 
of the simple distances. In his work on Mars, he 
? speaks of gravity as a mutual and corporeal affec- 
tion between similar bodies. He maintained that 
the tides were occasioned by the moon's attraction, 
and that the irregularities of the lunar motions, as 
detected by Tycho, were owing to the joint actions 
of the sun and the earth ; but the relation between 
gravity, as exhibited on the earth's surface, and as 
1 conducting the planets in their orbits, required 
more patience of thought than he could command, 
and was accordingly left for the exercise of higher 
powers. 

The misery in which Kepler lived forms a painful 
I contrast with the services which he performed to 
science. The pension on which he subsisted was 
always in arrears, and though the three emperors 
whose reigns he adorned directed their ministers 
to be more punctual in its payment, the disobe- 
dience of their commands was a source of continued 
vexation to Kepler. When he retired to Sagan, in 
Silesia, to spend in retirement the remainder of his 
days, his pecuniary difficulties became still more 
harassing. Necessity at last compelled him to apply 



124 SIR ISAAC NEWTON. 

personally for the arrears which were due ; and he 
accordingly set out in 1630 for Ratisbon; but in 
consequence of the great fatigue which so long a 
journey on horseback produced, he was seized with 
a fever, which carried him off on the 30th Novem- 
ber, 1630, in the 59th year of his age. 

While Kepler was thus laying the foundation of 
physical astronomy, Galileo was busily employed in 
extending the boundaries of the solar system. This 
distinguished philosopher was born at Pisa in 1564. 
He was the son of a Florentine nobleman, and was 
educated for the medical profession ; but a passion 
for geometry took possession of his mind, and called 
forth all his powers. Without the aid of a master, 
he studied the writings of Euclid and of Archimedes;; 
and such were his acquirements, that he was ap- 
pointed by the Grand-duke of Tuscany to the mathe- 
matical chair of Pisa in the twenty-fifth year of his 
age. His opposition to the Aristotelian philosophy 
gained him many enemies, and at the end of three 
years he quitted Pisa, and accepted of an invitation 
to the professorship of mathematics at Padua. Here 
he continued for eighteen years adorning the uni- 
versity by his name, and diffusing around him a 
taste for the physical sciences. With the excep- 
tion of some contrivances of inferior importance, 
Galileo had distinguished himself by no discovery 
till he had reached the forty-fifth year of his age. 
In the year 1609, the same year in which Kepler 
published his celebrated commentary on Mars, Gali- 
leo paid a visit to Venice, where he heard, in the 
course of conversation, that a Dutchman of the 
name of Jansens had constructed and presented to 
Prince Maurice an instrument through which he saw 
distant objects magnified and rendered more distinct, 
as if they had been brought nearer to the observer. 
This report was credited by some and disbelieved 
by others ; but, in the course of a few days, Galileo 
received a letter from James Badovere at Paris, 



GALILEO. 120 

which placed beyond a doubt the existence of such 
an instrument. The idea instantly filled his mind 
as one of the utmost importance to science ; and so 
thoroughly was he acquainted with the properties 
of lenses, that he not only discovered the principle 
of its construction, but was able to complete a tele- 
scope for his own use. Into one end of a leaden 
tube he fitted a spectacle-glass plane on one side 
and convex on the other, and in the other end he 
placed another spectacle-glass concave on one side 
and plane on the other. He then applied his eye 
to the concave glass, and saw objects "pretty large 
and pretty near him." They appeared three times 
nearer, and nine times larger in surface, than to the 
naked eye. He soon after made another, which 
represented objects above sixty times larger ; and, 
sparing neither labour nor expense, he finally con- 
structed an instrument so excellent, as "to show 
things almost a thousand times larger, and above 
thirty times nearer to the naked eye." 

There is, perhaps, no invention that science has 
presented to man so extraordinary in its nature, and 
| so boundless in its influence, as that of the tele- 
I scope. To the uninstructed mind, the power of 
jj seeing an object a thousand miles distant, as large 
I and nearly as distinct as if it were brought within 
I a mile of ,the observer, must seem almost miracu- 
t lous ; and to the philosopher, even, who thoroughly 
1 comprehends the principles upon which it acts, it 
I must ever appear one of the most elegant applica* 
| tions of science. To have been the first astronomer 
|i in whose hands such a gift was placed w r as a prefer- 
i| ence to which Galileo owed much of his future 
reputation. 

No sooner had he completed his telescope than 
he applied it to the heavens, and on the 7th Janu- 
ary, 1618, the first day of its use, he saw round 
Jupiter three bright little stars lying in a line par- 
allel to the ecliptic, two to the east, and one to the 
L2 



126 SIR ISAAC NEWTON. 

west of the planet. Regarding them as ordinary 
stars, he never thought of estimating their distances. 
On the following day, when he accidentally directed 
his telescope to Jupiter, he was surprised to see 
the three stars to the west of the planet. To pro- 
duce this effect it was requisite that the motion of 
Jupiter should be direct, though, according to calcu- 
lation, it was actually retrograde. In this dilemma 
he waited with impatience for the evening of the 
9th, but unfortunately the sky was covered with 
clouds. On the 10th he saw only two stars to the 
east a circumstance which he was no longer able 
to explain by the motion of Jupiter. He was there- 
fore compelled to ascribe the change to the stars 
themselves ; and upon repeating his observations 
on the llth, he no longer doubted that he had dis- 
covered three planets revolving round Jupiter. On 
the 13th January he for the first time saw the 
fourth satellite.* 

This discovery, though of the utmost importance 
in itself, derived an additional value from the light 
which it threw on the true system of the universe. 
While the earth was the only planet enlightened 
by a moon, it might naturally be supposed that it 
alone was habitable, and was therefore entitled to 
the pre-eminence of occupying the centre of the 
system ; but the discovery of four moons round a 
much larger planet deprived this argument of its 
force, and created a new analogy between the earth 
and the other planets. When Kepler received the 
" Sidereal Messenger," the work in which Galileo 
announced his discovery in 1610, he perused it with 
the deepest interest ; and while it confirmed and 
extended his substantial discoveries, it dispelled at; 
the same time some of those harmonic dreams which 
still hovered among his thoughts. In the "Dis- 

* Simon Marius, mathematician to the Marquis of Brandenburg, 
assures us that he discovered the satellites of Jupiter in November 
1609. 



GALILEO. 127 

sertation" which he published on the discovery of 
Galileo, he expresses his hope that satellites will 
be discovered round Saturn and Mars, he conjec- 
tures that Jupiter has a motion of rotation about 
his axis, and states his surprise, that, after what 
had been written on the subject of telescopes by 
Baptista Porta, they had not been earlier introduced 
into observatories. 

In continuing his observations, Galileo applied 
his telescope to Venus, and in 1610 he discovered 
the phases of that planet, which exhibited to him 
the various forms of the waxing and the waning 
moon. This fact established beyond a doubt that 
the planet revolved round the sun, and thus gave 
an additional blow to the Ptolemaic system. In his 
observations on the sun, Galileo discovered his spots, 
and deduced from them the rotation of the central 
luminary. He observed that the body of Saturn 
had handles attached to it ; but he was unable to 
detect the form of its ring, or render visible its 
minute satellites. On the surface of the moon he 
discovered her mountains and valleys, and deter- 
mined the curious fact of her libration, in virtue of 
which parts of the margin of her disk occasionally 
appear and disappear. In the Milky Way he de- 
scried numerous minute stars which the unassisted 
eye was unable to perceive ; and as the largest fixed 
stars, in place of being magnified by the telescope, 
became actually minute brilliant points, he inferred 
their immense distance as rendered necessary by the 
Copernican hypothesis. All his discoveries, indeed, 
furnished fresh arguments in favour of the new 
system ; and the order of the planets and their re- 
lation to a central sun may now be considered as 
established by incontrovertible evidence. 

While Galileo was occupied with these noble pur- 
suits at Pisa, to which he had been recalled in 1611, 
his generous patron, Cosmo II. Grand-duke of Tus- 
cany, invited him to Florence, that he might purmie 



128 SIR ISAAC NEWTON. 

with uninterrupted leisure his astronomical obser- 
vations, and carry on his correspondence with the 
German astronomers. His fame had now resounded 
through all Europe ; the strongholds of prejudice 
and ignorance were unbarred ; and the most obsti- 
nate adherents of ancient systems acknowledged 
the meridian power of the day-star of science. 
Galileo was ambitious of propagating the great 
truths which he contributed so powerfully to estab- 
lish. He never doubted that they would be re- 
ceived with gratitude by all, by the philosopher as 
the -consummation of the greatest efforts of human 
genius, and by the Christian as the most transcend- 
ent displays of Almighty power. But he had mis- 
taken the disposition of his species, and the charac- 
ter of the age. That same system of the heavens 
which had been discovered by the humble eccle- 
siastic of Frauenberg, which had been patronised by 
the kindness of a bishop, and .published at the ex- 
pense of a cardinal, and which the pope himself 
had sanctioned by the warmest reception, was, after 
the lapse of a hundred years, doomed to the most 
violent opposition, as subversive of the doctrines 
of the Christian faith. On no former occasion has 
the human mind exhibited such a fatal relapse into 
intolerance. The age itself had improved in libe- 
rality ; the persecuted doctrines themselves had 
become more deserving of reception ; the light of 
the Reformed faith had driven the Catholics from 
some of their most obnoxious positions ; and yet, 
under all these circumstances, the church of Rome 
unfurled her banner of persecution against the pride 
of Italy, against the ornament of his species, and 
against truths immutable and eternal. 

In consequence of complaints laid before the Holy 
Inquisition, Galileo was summoned to appear at 
Rome in 1615, to answer for the heretical opinions 
which he had promulgated. He was charged with 
M maintaining: as true the false doctrine held by 



GALILEO. 129 

many, that the sun was immoveable in the centre 
of the world, and that the earth revolved with a 
diurnal motion; with having certain disciples to 
whom he taught the same doctrine ; with keeping 
up a correspondence on the subject with several 
German mathematicians; with having published 
letters on the solar spots, in which he explained the 
same doctrine as true ; and with having glossed 
over with a false interpretation the passages of 
Scripture which were urged against it." The con- 
sideration of these charges came before a meeting 
of the Inquisition, which assembled on the 25th 
February, 1616 ; and the court, declaring their dis- 
position to deal gently with the prisoner, pro- 
aounced the following decree : " That Cardinal 
Bellarmine should enjoin Galileo to renounce en- 
;irely the above-recited false opinions ; that, on his 
'efusal to do so, he should be commanded by the 
commissary of the Inquisition to abandon the said 
doctrine, and to cease to teach and defend it ; and 
;hat, if he did not obey this command, he should 
>e thrown into prison." On the 26th of February 
alileo appeared before Cardinal Bellarmine, and, 
after receiving from him a gentle admonition, he 
was commanded by the commissary, in the presence 
of a notary and witnesses, to desist altogether from 
lis erroneous opinions ; and it was declared to be 
unlawful for him in future to teach them in any 
way whatever, either orally or in his writings. To 
these commands Galileo promised obedience, and 
was dismissed from the Inquisition. 

The mildness of this sentence was no doubt partly 
owing to the influence of the Grand-duke of Tus- 
cany, and other persons of rank and influence at the 
papal court, who took a deep interest in the issue 
of the trial. Dreading, however, that so slight a 
punishment might not have the eifect of putting 
down the obnoxious doctrines, the Inquisition issued 
a decree denouncing the new opinions as false and 



130 SIR ISAAC NEWTON. 

contrary to the sacred writings, and prohibiting the 
sale of eveiy book in which they should be main- 
tained. 

Thus liberated from his persecutors, Galileo re- 
turned to Florence, where he pursued his studies 
with his wonted diligence and ardour. The recanta- 
tion of his astronomical opinions was so formal 
and unreserved, that ordinary prudence, if not a 
sense of personal honour, should have restrained him 
from unnecessarily bringing them before the world. 
No anathema was pronounced against his scientific 
discoveries ; no interdict was laid upon the free 
exercise of his genius. He was prohibited merely 
from teaching a doctrine which the church of Rome 
considered to be injurious to its faith. We might 
have expected, therefore, that a philosopher so con- 
spicuous in the eyes of the world would have re- 
spected the prejudices, however base, of an institu- 
tion whose decrees formed part of the law of the 
land, and which possessed the power of life and 
death within the limits of its jurisdiction. Galileo, 
however, thought otherwise. A sense of degrada- 
tion* seems to have urged him to retaliate, and before 
six years had elapsed, he began to compose his 
" Cosmical System, or Dialogues on the two greatest 
Systems of the World, the Ptolemean and the Co- 
pernican," the concealed object of which is to 
establish the opinions which he had promised to 
abandon. In this work the subject is discussed by 
three speakers, Sagredo, Salviatus, and Simplicius, 
a peripatetic philosopher, who defends the system of 

* It is distinctly stated in the sentence of the Inquisition, that Galileo's 
enemies had charged him with having abjured his opinions in 1616, and 
affirmed that he had been punished by the Inquisition. In order to re- 
fute these calumnies, Galileo applied to Cardinal Bellarmine for a certifi- 
cate to prove that he neither abjured his opinions nor suffered any pun- 
ishment for them ; but that the doctrine of the motion of the earth .and 
the stability of the sun was only denounced to him as contrary to Scrip- 
ture, and as one which could not be defended or maintained. Cardinal 
Bellarmine drew up such a certificate in his own handwriting. 



GALILEO. 131 

Ptolemy with much skill against the overwhelming 
arguments of the rival disputants. Galileo hoped to 
escape notice by this indirect mode of propagating 
the new system, and he obtained permission to pub- 
lish his work, which appeared at Florence in 1632. 

The Inquisition did not, as might have been ex- 
pected, immediately summon Galileo to their pres- 
3nce. Nearly a year elapsed before they gave any 
ndication of their design; and, according to their 
own statement, they did not even take the subject 
under consideration till they saw that the obnoxious 
tenets were every day gaining ground, in conse- 
quence of the publication of the Dialogues. They 
then submitted the work to a careful examination, 
and having found it to be a direct violation of the 
njunction which had been formerly intimated to its 
author, they again cited him before their tribunal in 
1633. The venerable sage, now in his seventieth 
year, was thus compelled to repair to Rome, and 
when he arrived he was committed to the apart- 
ments of the Fiscal of the Inquisition. The un- 
changeable friendship, however, of the Grand-duke 
of Tuscany obtained a remission of this severity, 
and Galileo was allowed to reside at the house of 
:he Tuscan ambassador during the two months 
which the trial occupied. When brought before 
ihe Inquisition, and examined upon oath, he ac- 
knowledged that the Dialogues were written by him- 
self, and that he obtained permission to publish them 
without notifying to the person who gave it that he 
lad been prohibited from holding, defending, or 
teaching the heretical opinions. He confessed also 
ihat the Dialogues were composed in such a manner, 
ihat the arguments in favour of the Copernican sys- 
tem, though given as partly false, were yet managed 
in such a manner that they were more likely to con- 
firm than overturn its doctrines ; but that this error, 
which was not intentional, arose from the natural 
desire of making an ingenious defence of false propo- 



132 SIR ISAAC NEWTON. 

sitions, and of opinions that had the semblance of 
probability. 

After receiving these confessions and excuses, the 
Inquisition allowed Galileo a proper time for giving 1 
in his defence ; but this seems to have consisted 
solely in bringing forward the certificate of Cardinal 
Bellarmine already mentioned, which made no allu- 
sion to the promise under which Galileo had come 
never to defend, nor teach in any way whatever, the 
Copernican doctrines. The court held this defence 
to be an aggravation of the crime rather than an 
excuse for it, and proceeded to pronounce a sentence 
which will be ever memorable in the history of the 
human mind. 

Invoking the name of our Saviour, they declare, 
that Galileo had made himself liable to the suspicion 
of heresy, by believing the doctrine, contrary to 
Scripture, that the sun was the centre of the earth's 
orbit, and did not move from east to west ; and by 
defending as probable the opinion that the earth 
moved, and was not the centre of the world ; and 
that he had thus incurred all the censures and penal- 
ties which were enacted by the church against such 
offences ; but that he should be absolved from these 
penalties, provided he sincerely abjured and cursed 
all the errors and heresies contained in the formula 
of the church, which should be submitted to him. 
That so grave and pernicious a crime should not 
pass altogether unpunished, that he might become 
more cautious in future, and might be an example 
to others to abstain from such offences, they decreed 
that his Dialogues should be prohibited by a formal 
edict, that he should be condemned to the prison 
of the Inquisition during pleasure, and that, during 
the three following years, he should recite once a 
week the seven penitential psalms. 

This sentence was subscribed by seven cardinals ; 
and on the 22d June, 1633, Galileo signed an abjura- 
tion humiliating to himself and degrading to philoso- 



GALILEO. 133 



134 SIR ISAAC NEWTON. 

January, 1615, he defends the Copernican system 
with much boldness and ingenuity; he reconciles 
the various passages of Scripture with the new doc- 
trine, and he expresses the hope that such an attempt, 
now made for the first time, will prove agreeable to 
philosophers, but particularly to those very learned 
men, Galileo Galilei, John Kepler, and all the mem- 
bers of the Lyncean Academy, who, he believes, 
entertain the same opinion. This remarkable pro- 
duction, written from the convent of the Carmelites 
at Naples, is dedicated to the very Reverend Sebas- 
tian Fantoni, general of the order of Carmelites, and 
was published at Florence, with the sanction of the 
ecclesiastical authorities, in 1630 ; three years before 
the second persecution of Galileo. 

It would be interesting to know the state of public 
feeling in Italy when Galileo was doomed to the 
prisons of the Inquisition. No appeal seems to have 
been made against so cruel a sentence ; and neither 
in remonstrance nor in derision does an individual 
voice seem to have been raised. The master spirits 
of the age looked with sullen indifference on the 
persecution of exalted genius ; and Galileo lay in 
chains, deserted and unpitied. This unrebuked tri- 
umph of his enemies was perhaps favourable to the 
object of their vengeance. Resistance might have 
heightened the rigour of a sentence, which submis- 
sion seems to have alleviated. The interference 
of some eminent individuals of Rome, among whom 
we have no doubt that the Grand-duke of Tuscany 
was the most influential, induced Pope Urban VIII., 
not only to shorten the period, but to soften the 
rigour of Galileo's imprisonment. From the dun- 
geon of the Inquisition, where he had remained only 
foui days, he was transported to the ambassador's 
palace in the Garden de Medici at Rome ; and when 
his health had begun to suifer, he was permitted to 
leave the metropolis ; and would have been allowed 
to return to Florence, but as the plague raged in 



GALILEO. 135 

that city, he was sent, in July, 1633, to the archi- 
episcopal palace of Sienna, the residence of the Arch- 
bishop Piccolimini, where he carried on and com- 
pleted his valuable investigations respecting the 
resistance of solids. Here he continued five months, 
when, in consequence of the disappearance of the 
plague at Florence, he was allowed to retire to his 
villa at Bellosguardo, and afterward to that of Ar- 
cetri in the vicinity of Florence. 

Though Galileo was now, to a certain degree, 
liberated from the power of man, yet the afflicting 
dispensations of Providence began to fall thickly 
around him. No sooner had he returned to Arcetri, 
than his favourite daughter, Maria, was seized with 
a dangerous illness, which soon terminated in her 
death. He was himself attacked with hernia, pal- 
pitation of the heart, loss of appetite, and the most 
oppressive melancholy; and though he solicited 
permission to repair to Florence for medical assist- 
ance, yet this deed of mercy was denied him. In 
1638, however, the pope permitted him to pay a visit 
to Florence, and his friend, Father Castelli, was 
allowed to visit him in the company of an officer of 
the Inquisition. But this indulgence was soon with- 
drawn, and at the end of a few months he was re- 
manded to Arcetri. The sight of his right eye had 
begun to fail in 1636, from an opacity of the cornea. 
In 1637 his left eye was attacked with the same 
complaint ; so that in a few months he was affected 
with total and incurable blindness. Before this ca- 
lamity had supervened, he had noticed the curious 
phenomenon of the moon's libration, in consequence 
of which, parts of her visible disk that are exposed 
to view at one time are withdrawn at another. He 
succeeded in explaining two of the causes of this 
curious phenomenon, viz. the different distances of 
the observer from the line joining the centre of .the 
earth and the moon, which produces the diurnal 
libration, and the unequal motion of the moon in her 



136 



SIR ISAAC NEWTON. 



orbit, which produces the libration in longitude. It 
was left, however, to Hevelius to discover the libra- 
tion in latitude, which arises from the inclination of 
her axis being a little less than a right angle to the 
ecliptic ; and to Lagrange to discover the spheroidal 
libration, or that which arises from the action of the 
earth upon the lunar spheroid. 

The sorrows with which Galileo was now beset, 
seemed to have disarmed the severity of the Inqui- 
sition. He was freely permitted to enjoy the society 
of his friends, who now thronged around him to 
express their respect and their sympathy. The 
Grand-duke of Tuscany was his frequent visiter, 
and Gassendi, Deodati, and our countryman Milton 
went to Italy for the purpose of visiting him. He 
entertained his friends with the warmest hospitality, 
and though simple and abstemious in his diet, yet he 
was fond of good wine, and* seems even in his last 
days to have paid particular attention to the excel- 
lence of his cellar. 

Although Galileo had nearly lost his hearing as 
well as his sight, yet his intellectual faculties were 
unimpaired; and while his mind was occupied in 
considering the force of percussion, he was seized 
with fever and palpitation of the heart, which, after 
two months' illness, terminated his life on the 8th 
of January, 1642. 

Among the predecessors of Newton in astro- 
nomical research we must not omit the names of 
Bouillaud (Bullialdus), Borelli, and Dr. Hooke. 
Ismael Bouillaud, a native of Laon in France, and 
the author of several valuable astronomical works, 
has derived more reputation from a single -sentence 
in his Astronomica Philolaica, published in 1645, than 
from all the rest of his labours. He was not a be- 
liever in the doctrine of attraction, which, as we 
have already seen, had been broached by Copernicus, 
and discovered by Kepler ; but in speaking of that 
power as the cause of the planetary motions, he 



BORELLI HOOKE. 137 

remarks, "that if attraction existed, it would de- 
crease as the square of the distance." The influ- 
ence of gravity was still more distinctly developed 
by Borelli, a Neapolitan philosopher, who published 
h 1666 a work on Jupiter's satellites.* In this work 
he maintains, that all the planets perform their mo- 
tions round the sun according- to a general law ; that 
the satellites of Jupiter and of Saturn move round 
their primary planets in the same manner as the 
moon does round the earth, and that they all re- 
volve round the sun, which is the only source of 
any virtue, and that this virtue attaches them, and 
unites them so that they cannot recede from their 
centre of action, f 

Our countryman Dr. Robert Hooke seems to 
have devoted much of his attention to the cause of 
the planetary motions. On the 21st March, 1666, 
he read to the Royal Society an account of a series 
of experiments for determining if bodies experience 
any variation in their weight at different distances 
from the centre of the earth. His experiments, as 
Hooke himself saw, were by no means satisfactory, 
and hence he was led to the ingenious idea of 
measuring the force of gravity by observing, at dif- 
ferent altitudes, the rate of a pendulum clock. 
About two months afterward, he exhibited to the 
Society an approximate representation of the forces 
which retain the planets in their orbits, in the paths 
described by a circular pendulum impelled with dif- 

* TheorictB Medicearum planetarum ex causis physicis deducts 
Flor 1666, 4to. 

t M. Delambre maintains that these views of Borelli are only those of 
Kepler slightly modified. Newton and Huygens have attached to them 
a greater value. The last of these philosophers remarks, " Refert Plu- 
tarchus, fuisse jam olim qui putaret ideo manere lunam in orbe suo, quod 
vis recedendi a terra, ob motum circularem, inhiberetur pan vi gravi- 
tatis, qua ad terram accedere conaretur. Idemque aevo nostro, non de 
lunatantum sed et planetis ceteris statuit Alphonsus Borellus, utnempe 
primariis eorum gravitas esset solem versus ; lunis vero ad terram, 
Jovemac Saturnum quos comitantiir." Huygen, Cosmotheor, lib .; 
Opera, t. ii. p. 720. 

M2 



138 SIR ISAAC NEWTON. 

ferent degrees of force ; but though this experiment 
illustrated the production of a curvilineal motion, by 
combining a tangential force with a central power 
of attraction, yet it was only an illustration, and 
could not lead to the true cause of the planetary mo- 
tions. At a later period, however, viz. in 1674, 
Hooke resumed the subject in a dissertation entitled 
" An Attempt to prove the Motion of the Earth from 
Observation," which contains the following remark- 
able observations upon gravity: 

" I shall hereafter explain a system of the world 
differing in many particulars from any yet known, 
answering in all things to the common rules of me- 
chanical motions. This depends upon three suppo- 
sitions: first, that all celestial bodies whatsoever 
have an attraction or gravitating power towards 
their own centres, whereby they attract, not only 
their own parts, and keep them from flying from 
them, as we may observe the earth to do, but that 
they also do attract all the other celestial bodies 
that are within the sphere of their activity, and con- 
sequently, that not only the sun and moon have an 
influence upon the body and motion of the earth, 
and the earth upon them, but that Mercury, Venus, 
Mars, Jupiter, and Saturn, also, by their attractive 
powers, have a considerable influence upon its mo- 
tion, as in the same manner the corresponding at- 
tractive power of the earth hath a considerable in- 
fluence upon every one of their motions also. The 
second supposition is this, that all bodies what- 
soever that are put into a direct and simple motion 
will so continue to move forward in a straight line, 
till they are, by some other effectual powers, de- 
flected, and sent into a motion describing a circle, 
ellipsis, or some other more compounded curve line. 
The third supposition is, that those attractive pow- 
eis are so much the more powerful in operating by 
how much the nearer the body wrought upon is to their 
own centres. Now 9 what these several degrees are 1 



LAW OF GRAVITY. 130 

have not yet 'experimentally verified ; but it is a notion 
which, if ftey prosecute^ as it ought to be, will 
mightily assist the astronomers to reduce all the 
celestial motions to a certain rule, which I doubt 
will never be done without it. He that understands 
the nature of the circular pendulum and circular 
motion will easily understand the whole of this 
principle, and will know where to find directions in 
nature for the true stating thereof. This I only 
hint at present to such as have ability and opportu- 
nity of prosecuting this inquiry, and are not wanting 
of industry for observing and calculating, wishing 
heartily such may be found, having myself many 
other things in hand, which I would first complete, 
and therefore cannot so well attend it. But this I 
do not promise the undertaker, that he will find all 
the great motions of the world to be influenced by 
this principle, and that the true understanding 
thereof will be the true perfection of astronomy." 
This passage, which has been considered as a re- 
markable one by the philosophers of every country, 
has, we think, been misapprehended by M. Delam- 
bre, when he asserts that every thing which it con- 
tains " is to be found expressly in Kepler."* 

* Hist, de VA&tronomie aux Dioc-huitieme Sttcle, p. 9. 



140 SIR ISAAC NEWTON. 



CHAPTER XL 

The first Idea of Gravity occurs to Newton in 1666 His first Specu- 
lations upon itInterrupted by his Optical Experiments He re- 
sumes the Subject in consequence of a Discussion with Dr. Heoke 
He. discovers the true Law of Gravity and the Cause oftfie Planetary 
Motions Dr. Halley urges him to publish his Principia His Prin- 
ciples of Natural Philosophy Proceedings of the Royal Society on 
this Subject The Principia appears in 16S7 General Account of it, 
and of the Discoveries it contains They meet with great Opposition, 
owing to the Prevalence of the Cartesian System Account of the Re- 
ception and Progress of the Newtonian Philosophy in foreign Coun- 
tries Account of its Progress and Establishment in England. 

SUCH is a brief sketch of the labours and lives of 
those illustrious men who prepared the science of 
astronomy for the application of Newton's genius. 
Copernicus had determined the arrangement and 
general movements of the planetary bodies : Kepler 
had proved that they moved in elliptical orbits ; 
that their radii vectores described arcs proportional 
to the times; and that their periodic times wer 
related to their distances. Galileo had added to the 
universe a whole system of secondary planets ; and 
several astronomers had distinctly referred the mo- 
tion of the heavenly bodies to the power of attraction. 

In the year 1666, when the plague had driven 
Newton from Cambridge, he was sitting alone in 
the garden at Woolsthorpe, and reflecting on the 
nature of gravity, that remarkable power which 
causes all bodies to descend 'towards the centre of 
the earth. As this power is not found to suffer any 
sensible diminution at the greatest distance from 
the earth's centre to which we can reach, being as 
powerful at the tops of the highest mountains as at 
the bottom of the deepest mines, he conceived it 
highly probable, that it must extend much farther 
than was usually supposed. No sooner had this 



NEWTON'S IDEA OF GRAVITY. lit 

conjecture occurred to his mind, than he con- 
le'red what would be the effect of its extending as 
far as the moon. That her motion must be influ- 
enced by such a power he did not for a moment 
doubt ; and a little reflection convinced him that it 
might be sufficient for retaining that luminary in her 
orbit round the earth. Though the force of gravity 
suffers no sensible diminution at those small dis- 
tances from the earth's centre at which we can 
place ourselves, yet he thought it very possible, 
that, at the distance of the moon, it might, differ 
much in strength from what it is on the earth. In 
order to form some estimate of the degree of its 
diminution, he considered that, if the moon be re- 
tained in her orbit by the force of gravity, the pri- 
mary planets must also be carried round the sun by 
the same power ; and by comparing the periods of 
the different planets with their distances from the 
sun, he found, that if they were retained in their 
orbits by any power like gravity, its force must de- 
crease in the duplicate proportion,* or as the squares 
of their distances from the sun. In drawing this 
conclusion, he supposed the planets to move in or- 
bits perfectly circular, and having the sun in their 
centre. Having thus obtained the law of the force 
by which the planets were drawn to the sun, his 
next object was to ascertain if such a force, ema- 
nating from the earth and directed to the moon, was 
sufficient, when diminished in the duplicate ratio of 
the distance, to retain her in her orbit. In perform- 
ing this calculation, it was necessary to compare 
the space through which heavy bodies fall in a second 
at a given distance from the centre of the earth, viz. 
at its surface, with the space through which the 
moon, as it were, falls to the earth in a second of 
time while revolving in a circular orbit. Being at 

* " But for the duplicate proportion, I gathered it from Kepler's theo- 
rem about twenty years ago." Newton's Letter to Halley, July 14, 1686. 



142 SIR ISAAC NEWTON. 

a distance from books when he made this compu- 
tation, he adopted the common estimate of the earth's 
diameter then in use among geographers and navi- 
gators, and supposed that each degree of latitude 
contained sixty English miles. In this way he 
found that the force which retains the moon in her 
orbit, as deduced from the force which occasions the 
fall of heavy bodies to the earth's surface, was one- 
sixth greater than that which is actually observed in 
her circular orbit. This difference threw a doubt 
upon all his speculations ; but, unwilling to abandon 
what seemed to be otherwise so plausible, he endeav- 
oured to account for the difference of the two forces, 
by supposing that some other cause* must have been 
united with the force of gravity in producing so 
great a velocity of the moon in her circular orbit. 
As this new cause, however, was beyond the reach 
of observation, he discontinued all further inquiries 
into the subject, and concealed from his friends the 
speculations in which he had been employed. 
^ After his return to Cambridge in 1666, his atten- 
tion was occupied with those optical discoveries of 
which we have given an account in a preceding 
chapter ; but he had no sooner brought them to a 
close than his mind reverted to the great subject of 
the planetary motions. Upon the death of Olden- 
burg in August, 1678, Dr. Hooke was appointed 
secretary to the Royal Society ; and as this learned 
body had requested the opinion of Newton about a 
system of physical astronomy, he addressed a letter 
to Dr. Hooke on the 28th November, 1679. In this 
letter he proposed a direct experiment for verifying 
the motion of the earth, viz. by observing whether 
or not bodies that fall from a considerable height 
descend in a vertical direction, for if the earth were 
at rest the body would describe exactly a vertical 

* Whiston asserts that this cause was supposed by Newton to be 
something analogous to the vortices of Descartes. See Whiston's Me- 
moirs of himself, p. 231. 



LAW OF GRAVITY. 143 

line, whereas if it revolved round its axis, the falling 
body must deviate from the vertical line towards the 
east. The Royal Society attached great value to * 
the idea thus casually suggested, and Dr. Hooke was 
appointed to put it to the test of experiment. Being 
thus led to consider the subject more attentively, he 
wrote to Newton, that wherever the direction of 
gravity was oblique to the axis on which the earth 
revolved, that is, in every part of the earth ex- 
cept the equator, falling bodies should approach 
to the equator, and the deviation from the ver- 
tical, in place of being exactly to the east, as 
Newton maintained, should be to the south-east of ~ 
the point from which the body began to move. 
Newton acknowledged that this conclusion was cor- 
rect in theory, and Dr. Hooke is said to have given 
an experimental demonstration of it before the Royal 
Society in December, 1679.* Newton had errone-^" 
ously concluded that the path of the falling body 
would be a spiral; but Dr. Hooke, on the same 
occasion on which he made the preceding experi- 
ment, read a paper to the Society, in which he proved 
that the path of the body would be an eccentric 
ellipse in vacuo, and an ellipti-spiral, if the body 
moved in a resisting medium-! 

This correction of Newton's error, and the dis- 
covery that a projectile would move in an elliptical 
orbit when under the influence of a force varying in 
the inverse ratio of the square of the distance, led 
Newton, as he himself informs us in his letter to 
Halley,J to discover " the theorem by which he af- 
terward examined the ellipsis," and to demonstrate 
the celebrated proposition, that a planet acted upon 
by an attractive force varying inversely as the 
squares of the distances will describe an elliptical 
orbit, in one of whose foci the attractive force re- 
sides. 

* Waller's Life of Hooke, p. 22. 
J July 27, 1686, Biog. Brit. p. 2662. 



144 SIR ISAAC NEWTON. 

But though Newton had thus discovered the true 
cause of all the celestial motions, he did not yet 
possess any evidence that such a force actually re- 
sided in the sun and planets. The failure of his 
former attempt to identify the law of falling bodies 
at the earth's surface with that which guided the 
moon in her orbit threw a doubt over all his specu- 
lations, and prevented him from giving any account 
of them to the public. 

* An accident, however, of a very interesting nature 
induced him to resume his former inquiries, and 
enabled him to bring them to a close. In June, 
1682, when he was attending a meeting of the Royal 
Society of London, the measurement of a degree of 
the meridian, executed by M. Picardin 1679, became 
the subject of conversation. Newton took a memo- 
randum of the result obtained by the French astron- 
omer, and having deduced from it the diameter of the 
earth, he immediately resumed his calculation of 
1665, and began to repeat it with these new data. 
In the progress of the calculation he saw that the 
result which he had formerly expected was likely to 
be produced, and he was thrown into such a state of 
nervous irritability that he was unable to carry on 
the calculation. In this state of mind he intrusted 
it to one of his friends, and he had the high satis- 
faction of finding his former views amply realized. 
The force of gravity which regulated the fall of 
bodies at the earth's surface, when diminished as 
the square of the moon's distance from the earth, 
was found to be almost exactly equal to the centri- 
L, fugal force of the moon as deduced from her observed 
distance and velocity. 

The influence of such a result upon such a mind 
maybe more easily conceived than described. The 
whole material universe was spread out before him ; 
the sun with all his attending planets ; the planets 
with all their satellites; the comets wheeling in 
every direction in their eccentric orbits ; and the 



PLANETARY MOTIONS. 145 

systems of the fixed stars stretching to the remotest 
limits of space. All the varied and complicated 
movements of the heavens, in short, must have been 
at once presented to his mind, as the necessary result 
of that law which he had established in reference to 
the earth and the moon. 

After extending this law to the other bodies of 
;he system, he composed a series of propositions 
on the motion of the primary planets about the siin^ 
which were sent to London about the end of 1683, 
and were soon afterward communicated to tfre 
[loj'al Society.* 

About this period other philosophers had been 
occupied with the same subject. Sir Christopher 
Wren had many years before endeavoured to ex- 
plain the planetary motions "by the composition 
of a descent towards the sun, and an impressed 
motion ; but he at length gave it over, not finding 
he means of doing it." In January, 1683-4, Dr. 
Galley had concluded, from Kepler's Law of the 
Periods and Distances, that the centripetal force de- 
Teased in the reciprocal proportion of the squares 
of the distances, and having one day met Sir Chris- 
;opher Wren and Dr. Hooke, the latter affirmed 
,hat he had demonstrated upon that principle all 
;he laws of the celestial motions. Dr. Halley con- 
r essed that his attempts were unsuccessful, and 
Sir Christopher, in order to encourage the inquiry, 
offered to present a book of forty shillings' value to 
either of the two philosophers who should, in the 
space of two months, bring him a convincing de- 
monstration of it. Hooke persisted in the decla- * 
ration that he possessed the method, but avowed it 
to be his intention to conceal it for some time. He 
promised, however, to show it to Sir Christopher ; 
but there is every reason to believe that this prom- 
ise was never fulfilled. 

In August, 1684,, Dr. Halley went to Cambridge 

* Commercium Epistolicum t No. 7 



'146 SIR ISAAC NEWTON. 

for the express purpose of consulting Newton on 
this interesting subject. Newton assured him that 
he had brought this demonstration to perfection, 
and promised him a copy of it. This copy was re- 
ceived in November by the doctor, who made a 
second visit to Cambridge, in order to induce its 
author to have it inserted in the register book of 
the society. On the 10th of December, Dr. Halley 
announced to the society, that he had seen at Cam- 
bridge Mr. Newton's treatise De Motu Corporum, 
which he had promised to send to the society to be 
entered upon their register ; and Dr. Halley was de- 
sired to unite with Mr. Paget, master of the mathe- 
matical school in Christ's Hospital, in reminding 
Mr. Newton of his promise " for securing the inven- 
tion to himself till such time as he can be at leisure 
to publish it." On the 25th February Mr. Aston, 
the secretary, communicated a letter from Mr. 
Newton, in which he expressed his willingness " to 
enter in the register his notions about motion, and 
his intentions to fit them suddenly for the press." 
The progress of his work was, however, interrupted 
by a visit of five or six weeks which he made in 
Lincolnshire ; but he proceeded with such diligence 
on his return, that he was able to transmit the manu- 
script to London before the end of April. This 
manuscript, entitled Philosophic Naturalis Principia 
Mathematica^ and dedicated to the society, was pre- 
sented by Dr. Vincent on the 28th April, 1686, when 
Sir John Hoskins, the vice-president, and the par- 
ticular friend of Dr. Hooke, was in the chair. Dr. 
Vincent passed a just encomium on the novelty and 
dignity of the subject ; and another member added, 
that " Mr. Newton had carried the thing so far, that 
there was no more to be added." To these remarks 
the vice-president replied, that the method " was so 
much the more to be prized as it was both invented 
and perfected at the same time." Dr. Hooke took 
offence at these remarks, and blamed Sir John for 



PRINCIPIA. 147 

ipt having mentioned " what he had discovered to 
lim ;" but the vice-president did not seem to recol- 
ect any such communication, and the consequence 
)f this discussion was, that " these two, who till 
hen were the most inseparable cronies, have since 
scarcely seen one another, and are utterly fallen 
>ut." After the breaking up of the meeting, the 
ociety adjourned to the coffee-house, where Dr. 
Hooke stated that he not only had made the same 
iiscovery, but had given the first hint of it to Newton. 
An account of these proceedings was communi- 
ated to Newton through two different channels, 
n a letter dated May 22d, Dr. Halley wrote to him 
that Mr. Hooke has some pretensions upon the 
nvention of the rule of the decrease of gravity be- 
ig reciprocally as the squares of the distances from 
le centre. He says you had the notion from him, 
lough he owns the demonstration of the curves 
enerated thereby to be wholly your own. How 
nuch of this is so you know best, as likewise what 
ou have to do in this matter. Only Mr. Hooke 
eems to expect you would make some mention of 
im in the preface, which it is possible you may 
ee reason to prefix." 

'This communication from Dr. Halley induced 

ur author, on the 20th June, to address a long 

itter to him, in which he gives a minute and able 

Mutation of Hooke's claims ; but before this letter 

as despatched, another correspondent, who had 

eceived his information from one of the members 

lat were present, informed Newton " that Hooke 

nade a great stir, pretending that he had all from 

im, and desiring they would see that he had justice 

one him." This fresh charge seems to have ruf- 

ed the tranquillity of Newton ; and he accordingly 

idded an angry and satirical postscript, in which he 

treats Hooke with little ceremony, and goes so far 

as to conjecture that Hooke might have acquired 

his knowledge of the law from a letter of his own 



148 SIR ISAAC NEWTON. 

to Huygens, directed to Oldenburg, and dated Janu- 
ary 14th, 1672-3. "My letter to Hugenius was 
directed to Mr. Oldenburg, who used to keep the 
originals. His papers came into Mr. Hooke's pos- 
session. Mr. Hooke, knowing my hand, might have 
the curiosity to look into that letter, and there take 
the notion of comparing the forces of the planets 
arising from their circular motion ; and so what he 
wrote to me afterward about the rate of gravity 
might be nothing but the fruit of my own garden." 

In replying to this letter, Dr. Halley assured him 
that Hooke's "manner of claiming the discovery 
had been represented to him in worse colours than 
it ought, and that he neither made public application 
to the society for justice, nor pretended that you 
had all from him." The effect of this assurance 
was to make Newton regret that he had written the 
angry postscript to his letter; and in replying to 
Halley on the 14th July, 1686, he not only expresses 
his regret, but recounts the different new ideas 
which he had acquired from Hooke's correspon- 
dence, and suggests it as the best method " of com- 
promising the present dispute," to add a scholium, 
in which Wren, Hooke, and Halley are acknowledged 
to have independently deduced the law of gravity 
from the second law of Kepler.* 

At the meeting of the 28th April, at which the 
manuscript of the Principia was presented to the 
Royal Society, it was agreed that the printing of it 
should be referred to the council ; that a letter of 
thanks should be written to its author; and at a 
meeting of the council on the 19th May, it was 
resolved that the MSS. should be printed at the 
society's expense, and that Dr. Halley should super- 
intend it while going through the press. These 
resolutions were communicated by Dr. Halley in a 
letter dated the 22d May ; and in Newton's replv on 
the 20th June already mentioned, he makes the fol 

* This Scholium is added to Prop. iv. lib. i. coroll 6. 



PRINCIPIA. 149 

towing observations : " The proof you sent me I 
like very well. I designed the whole to consist of 
three books ; the second was finished last summer, 
being short, and only wants transcribing, and draw- 
I trig the cuts fairly. Some new propositions I have 
bince thought on, which I can as well let alone. 
[The third wants the theory of comets. In autumn 
| last I spent two months in calculation to no purpose 
I for want of a good method, which made me after- 
[ward return to the first book, and enlarge it with 
[diverse propositions, some relating to comets, others 
| to other things found out last winter. The third I 
(now design to suppress. Philosophy is such an im- 
pertinently litigious lady, that a man had as good be 
I engaged in lawsuits as have to do with her. I 
found it so formerly, and now I can no sooner come 
near her again but she gives me warning. The first 
two books without the third will not so well bear 
the title of Philosophise, Naturalis Principia Mathe- 
\matica ; and therefore I had altered it to this, De 
\ Motu Corporum Libri duo. But after second thoughts 
il retain the former title. It will help the sale of the 
! book, which I ought not to diminish now 'tis yours." 
In replying to this letter on the 29th June, Dr. 
Halley regrets that our author's tranquillity should 
have been thus disturbed by envious rivals; and 
implores him in the name of the society not to 
suppress the third book. " I must again beg you," 
says he, " not to let your resentments run so high 
as to deprive us of your third book, wherein your 
applications of your mathematical doctrine to the 
theory of comets, and several curious experiments, 
which, as I guess by what you write ought to com- 
pose it, will undoubtedly render it acceptable to 
those who will call themselves philosophers without 
mathematics, which are much the greater number.'* 
To these solicitations Newton seems to have 
readily yielded. His second book was sent to the 
society, and presented on the 2d March, 1686-7. 



150 SIR ISAAC NEWTON. 

The third book was also transmitted, and presented 
on the 6th April, and the whole work was completed 
and published in the month of May, 1687. 

Such is a brief account of the publication of a 
work which is memorable, not only in the annals ofj 
one science or of one country, but which will form 
an epoch in the history of the world, and will ever 
be regarded as the brightest page in the records of 
human reason. We shall endeavour to convey to 
the reader some idea of its contents, and of the bril- 
liant discoveries which it disseminated over Europe. 

The Principia consists of three books. The first 
and second, which occupy three-fourths of the work, 
are entitled, On the Motion of Bodies ; and the third 
bears the title, On the System of the World. The 
first two books contain the mathematical principles 
of philosophy, namely, the laws and conditions of 
motions and forces ; and they are illustrated with 
several philosophical scholia, which treat of some ofj 
the most general and' best established points in phi- 
losophy, such as the density and resistance of bodies, 
spaces void of matter, and the motion of sound and 
light. The object of the third book is to deduce 
from these principles the constitution of the system 
of the world ; and this book has been drawn up in 
as popular a style as possible, in order that it may 
be generally read. 

The great discovery which characterizes the 
Principia is that of the principle of universal gravi- 
tation, as deduced from the motion of the moon, 
and from the threegreat facts or laws discovered Jby 
^Ke_pler. This principle is, that every~~pdriicle of 
matter is attracted by, or gravitates to, every other 
particle of matter, with a force inversely proportional 
to the squares of their distances. From the first law 
of Kepler, namely, the proportionality of the areas 
to the times of their description, Newton inferred 
that the force which kept the planet in its orbit was 
always directed to the sun; and from the second 



UNIVERSAL GRAVITATION. ll 

law of Kepler, that every planet moves in an ellipse 
i with the sun in one of its foci, he drew the still more 
general inference, that the force by which the planet 
Inoves round that focus varies inversely as the 
[square of its distance from the focus. As this law 
:was true in the motion of satellites round their pri- 
mary planets, Newton deduced the equality of gravity 
in all the heavenly bodies towards the sun, upon the 
supposition that they are equally distant from its 
centre ; and in the case of terrestrial bodies, he sue 
needed in verifying this truth by numerous and accu 
rate experiments. 

By taking a more general view of the subject 
Newton demonstrated that a conic section was the 
only curve in which a body could move when acted 
upon by a force varying inversely as the square of 
he distance ; and he established the conditions de- 
pending on the velocity and the primitive position 
of the body, which were requisite to make it de- 
scribe a circular, an elliptical, a parabolic, or a 
lyperbolic orbit. 

Notwithstanding the generality and importance 
of these results, it still remained to be determined 
whether the force resided in the centres of the 
)lanets, or belonged to each individual particle of 
which they were composed. Newton removed this 
incertainty by demonstrating, that if a spherical 
>ody acts upon a distant body with a force varying 
as the distance of this body from the centre of the 
phere, the same effect will be produced as if each 
>f its particles acted upon the distant body accord- 
ing to the same law. And hence it follows that the 
spheres, whether they are of uniform density, or 
consist of concentric layers, with densities varying 
according to any law whatever, will act upon each 
other in the same manner as if their force resided 
in their centres alone. But as the bodies of the 
solar system are very nearly spherical, they will all 
act upon one another, and upon bodies placed oa 



152 SIR ISAAC NEWTON. 

their surface, as if they were so many centres of 
attraction ; and therefore we obtain the law of gravity 
which subsists between spherical bodies, namely, 
that one sphere will act upon another with a force 
directly proportional to the quantity of matter, and 
inversely as the square of the distance between the 
centres of the spheres. From the equality of action 
and reaction, to which no exception can be found, 
Newton concluded that the sun gravitated to the 
planets, and the planets to their satellites ; and the 
earth itself to the stone which falls upon its surface; 
and, consequently, that the two mutually gravitating 
bodies approached to one another with velocities 
inversely proportional to their quantities of matter. 

Having established this universal law, Newton 
was enabled, not only to determine the weight which 
the same body would have at the surface of the sun 
and the planets, but even to calculate the quantity 
of matter in the sun, and in all the planets that had 
satellites, and even to determine the density or 
specific gravity of the matter of which they were 
composed. In this way he found that the weight of 
the same body would be twenty-three times greater 
at the surface of the sun than at the aurface of the 
earth, and that the density of the earth was four times 
greater than that of the sun, the planets increasing 
in density as they receded from the centre of the 
system. 

If the peculiar genius of Newton has been dis- 
played in his investigation of the law of universal 
gravitation, it shines with no less lustre in the pa- 
tience and sagacity with which he traced the conse- 
quences of this fertile principle. 

The discovery of the spheroidal form of Jupiter 
by Cassini had probably directed the attention of 
Newton to the determination of its cause, and con 
sequently to the investigation of the true figure of 
the earth. The spherical form of the planets have 
been ascribed by Copernicus to the gravity or natural 



FIGURE OF THE EARTH. 153 

itency of their parts; but upon considering the 
;h as a body revolving upon its axis, Newton 
quickly saw that the figure arising from the mutual 
attraction of its parts must be modified by another 
force arising from its rotation. When a body re- 
volves upon an axis, the velocity of rotation in- 
creases from the poles, where it is nothing, to the 
equator, where it is a maximum. In consequence 
of this velocity the bodies on the earth's surface 
[lave a tendency to fly off from it, and this tendency 
increases with the velocity. Hence arises a centrifu- 
gal force which acts in combination with a force 
of gravity, and which Newton found to be the 289th 
part of the force of gravity at the equator, and de- 
creasing, as the cosine of the latitude, from the 
equator to the poles. The great predominance of 
gravity over the centrifugal force prevents the latter 
irom carrying off any bodies from the earth's sur- 
face, but the weight of all bodies is diminished by 
;he centrifugal force, so that the weight of any body 
is greater at the poles than it is at the equator. If 
we now suppose the waters at the pole to commu- 
nicate with those at the equator by means of a ca- 
nal, one branch of which goes from the pole to the 
centre of the earth, and the other from the centre 
of the earth to the equator, then the polar branch 
of the canal will be heavier than the equatorial 
branch, in consequence of its weight not being di- 
minished by the centrifugal force, and, therefore, in 
order that the two columns maybe in equilibrio, the 
equatorial one must be lengthened. Newton found 
that the length of the polar must be to that of the 
equatorial canal as 229 to 230, or that the earth's polar 
radius must be seventeen miles less than its equa- 
jtorial radius ; that is, that the figure of the earth is 
an oblate spheroid, formed by the revolution of an 
ellipse round its lesser axis. Hence it follows, that 
the intensity of gravity at any point of the earth's 
surface is in the inverse ratio of the distance of that , 



154 SIR ISAAC NEWTON. 

point from the centre, and, consequently, that it di- 
minishes from the equator to the poles, a result 
which he confirmed by the fact, that clocks required 
to have their pendulums shortened in order to beat 
true time when carried from Europe towards the 
equator. 

The next subject to which Newton applied the 
principle of gravity was the tides of the ocean. 
The philosophers of all ages have recognised the 
connexion between the phenomena of the tides and 
the position of the moon. The College of Jesuits 
at Coimbra, and subsequently Antonio de Dominis 
and Kepler, distinctly referred the tides to the attrac- 
tion of the waters of the earth by the moon, but so 
imperfect was the explanation which was thus given 
of the phenomena, that Galileo ridiculed the idea of 
lunar attraction, and substituted for it a fallacious 
explanation of his own. That the moon is the 
principal cause of the tides is obvious from the well- 
known fact, that it is high water at any given place 
about the time when she is in the meridian of that 
place ; and that the sun performs a secondary part 
in their production may be proved from the circum- 
stance, that the highest tides take place when the 
sun, the moon, and the earth are in the same straight 
line, that is, when the force of the sun conspires 
with that of the moon, and that the lowest tides 
take place when the lines drawn from the sun and 
moon to the earth are at right angles to each other, 
that is, when the force of the sun acts in opposition 
to that of the moon. The most perplexing phe- 
nomenon in the tides of the ocean, and one which is 
still a stumbling-block to persons slightly acquainted 
with the theory of attraction, is the existence of 
high water on the side of the earth opposite to the 
moon, as well as on the side next the moon. To 
maintain that the attraction of the moon at the same 
instant draws the waters of the ocean towards her- 
self, and also draws them from the earth in an oppo- 



TIDES. 155 

ite direction, seems at first sight paradoxical ; but 
he difficulty vanishes when we consider the earth, 
r rather the centre of the earth, and the water on 
ach side of it as three distinct bodies placed at dif- 
erent distances from the moon, and consequently 
ttr acted with forces inversely proportional to the 
quaies of their distances. The water nearest the 
noon will be much more powerfully attracted than 
he centre of the earth, and the centre of the earth 
nore powerfully than the water farthest from the 
noon. The consequence of this must be, that the 
raters nearest the moon will be drawn away from 
he centre of the earth, and will consequently rise 
om their level, while the centre of the earth will 
e drawn away from the waters opposite the moon, 
vhich will, as it were, be left behind, and conse- 
uently be in the same situation as if they were 
aised from the earth in a direction opposite to 
lat in which they are attracted by the moon, 
"ence the effect of the moon's action upon the 
arth is to draw its fluid parts into the form of an 
)long spheroid, the axis of which passes through 
le moon. As the action of the sun will produce 
le very same effect, though in a smaller degree, 
le tide at any place will depend on the relative po- 
tion of these two spheroids, and will be always 
qual either to the sum or to the difference of the 
ffects of the two luminaries. At the time of new 
nd full moon the two spheroids will have their axes 
oincident, and the height of the tide, which will 
len be a spring one, will be equal to the sum of the 
evations produced in each spheroid considered 
Bparately, while at the first and third quarters the 
tes of the spheroids will be at right angles to each 
;her, and the height of the tide, which will tlien be 
ja neap one, will be equal to the difference of the 
elevations produced in each separate spheroid. By 
comparing the spring and neap tides, Newton found 
that the force with which the sun acted upon the 



156 SIR ISAAC NEWTON. 

waters of the earth was to that with which the sun ; 
acted upon them as 4.48 to 1 ; that the force of the | 
moon produced a tide of 8.63 feet ; that of the suni 
one of 1.93 feet; and both of them combined, one 
of 1(H French feet, a result which in the open sea 
does not deviate much from observation. Having 
thus ascertained the force of the moon on the waters 
of our globe, he found that the quantity of mattei 
in the moon was to that in the earth as 1 to 40, and 
the density of the moon to that of the earth as 11 
to 9. 

The motions of the moon, so much within the 
reach of our own observation, presented a fine field 
for the application of the theory of universal gravi- 
tation. The irregularities exhibited in the lunai 
motions had been known in the time of Hipparchus 
and Ptolemy. Tycho had discovered the great in- 
equality called the variation, amounting to 37', and 
depending on the alternate acceleration and retard- 
ation of the moon in every quarter of a revolution, 
and he had also ascertained the existence of the 
annual equation. Of these two inequalities Newton 
gave a most satisfactory explanation. The action 
of the sun upon the moon may be always resolved 
into two, one acting in the direction of the line join- 
ing the moon and earth, and consequently tending 
to increase or diminish the moon's gravity to the 
earth, and the other in a direction at right angles to 
this, and consequently tending to accelerate or re- 
tard the motion in her orbit. Now, it was found by 
Newton that this last force was reduced to nothing, 
or vanished at the syzigies or quadratures, so that 
at these four points the moon described areas pro- 
portional to the times. The instant, however, that 
the moon quits these positions, the force under con* 
sideration, which we may call the tangential force, 
begins, and it reaches its maximum in the four oc- 
tants. The force, therefore, compounded of these 
two elements of the solar force, or the diagonal of 



LUNAR THEORY. 157 

i the parallelogram which they form, is no longer 
directed to the earth's centre, but deviates from it at 
a maximum about 30 minutes, and therefore affects 
the angular motion of the moon, the motion being 
accelerated in passing from the quadratures to the 
syzigies, and retarded in passing from the syzigies 
to the quadratures. Hence the velocity is in its 
mean state in the cctanls, a maximum in the syzi- 
gies, and a minimum in the quadratures. 

Upon considering the influence of the solar force 
in diminishing or increasing the moon's gravity to 
the earth, Newton saw that her distance and her 
periodic time must from this cause be subject to 
change, and in this way he accounted for the annual 
equation observed by Tycho. By the application 
of similar principles, he explained the cause of the 
motion of the apsides, or of the greater axis of the 
moon's orbit, which has an angular progressive mo- 
tion of 3 4' nearly in the course of one lunation ; 
and he showed that the retrogradation of the nodes, 
amounting to 3' 10" daily, arose from one of the ele- 
ments of the solar force being exerted in the plane 
of the ecliptic, and not in the plane of the moon's 
orbit, the effect of which was to draw the moon 
down to the plane of the ecliptic, and thus cause the 
[me of the nodes, or the intersection of these two 
planes, to move in a direction opposite to that of the 
moon. The lunar theory thus blocked out by New- 
ton, required for its completion the labours of another 
century. The imperfections of the fluxionary cal- 
culus prevented him from explaining the other ine- 
qualities of the moon's motions, and it was reserved 
to Euler, D'Alembert, Clairaut, Mayer, and Laplace 
to bring the lunar tables to a high degree of perfec- 
tion, and to enable the navigator to determine his 
longitude at sea with a degree of precision which 
the most sanguine astronomer could scarcely have 
anticipated. 

By the consideration of the retrograde motion of 
O 



158 SIR ISAAC NEWTOff. 

the moon's nodes, Newton was led to discover the 
cause of the remarkable phenomenon of the preces- 
sion of the equinoctial points, which moved 50" an- 
nually, and completed the circuit of the heavens in 
25,920 years. Kepler had declared himself incapa- 
ble of assigning- any cause for this motion, and we 
do not believe that any other astronomer ever made 
the attempt. From the spheroidal form of the earth, 
it may be regarded as a sphere with a spheroidal 
ring surrounding its equator, one-half of the ring 
beii^ "ibove the plane of the ecliptic and the other 
half below it. Considering this excess of matter 
as a system of satellites adhering to the earth's sur- 
face, Newton saw that the combined actions of the 
sun and moon upon these satellites tended to pro- 
duce a retrogradation in the nodes of the circles 
which they described in their diurnal rotation, and 
that the sum of all the tendencies being communi- 
cated to the whole mass of the planet, ought to pro- 
duce a slow retrogradation of the equinoctial points. 
The effect produced by the motion of the sun he 
found to be 40", and that produced by the action of , 
the moon 10". 

Although there could be little doubt that the 
comets were retained in their orbits by the same 
laws which regulated the motions of the planets, 
yet it was difficult to put this opinion to the test of 
observation. The visibility of comets only in a 
small part of their orbits rendered it difficult to as- , 
certain their distance and periodic times, and as theii 
periods were probably of great length, it was impos- \ 
sible to correct approximate results by repeated ob- 
servation. Newton, however, removed this diffi- j 
culty, by showing how to determine the orbit of 2 i 
comet, namely, the form and position of the orbil i 
and the periodic time, by three observations. By [ 
applying this method to the comet of 1680, he cal- 
culated the elements of its orbit, and from the agree- 
ment of the comouted places with those which 



COMETS. 159 

vere observed, he justly inferred that the motions 
)f comets were regulated by the same laws as those 
>f the planetary bodies. This result was one of 
preat importance ; for as the comets enter our sys- 
em in every possible direction, and at all angles 
vith the ecliptic, and as a great part of their orbits 
xtend far beyond the limits of the solar system, it 
emonstrated the existence of gravity in spaces far 
removed beyond the planet, and proved that the law 
)f the inverse ratio of the squares of the distance 
Fas true in every possible direction, and at very re- 
note distances from the centre of our system.* 
Such is a brief view of the leading discoveries 
r hich the Principia first announced to the world. 
The grandeur of the subjects of which it treats, the 
eautiful simplicity of the system which it unfolds, 
he clear and concise reasoning by which that sys- 
,em is explained, and the irresistible evidence by 
ivhich it is supported might have ensured it the 
warmest admiration of contemporary mathemati- 
ians, and the most welcome reception in all the 
chools of philosophy throughout Europe. This, 
lowever, is not the way in which great truths are 
generally received. Though the astronomical dis- 
overies of Newton were not assailed by the class 
>f ignorant pretenders who attacked his optical 
writings, yet they were every where resisted by the 
rrors and prejudices which had taken a deep hold 
ven of the strongest minds. The philosophy of 
Descartes was predominant throughout Europe. 
Appealing to the imagination, and not to the reason 
f mankind, it was quickly received into popular 
avour, and the same causes which facilitated its in- 
roduction extended its influence, and completed its 
ominion over the human mind. In explaining all 
the movements of the heavenly bodies by a system 

* In writing to Flamstead, Newton requests from him the long diame- 
ters of the orbits cf Jupiter and Saturn, that he " may see how the ses* 
guialt&raJ proportion Jills the heavens.'' 



160 SIR ISAAC NEWTON. 

of vortices in a fluid medium diffused through the 
universe, Descartes had seized upon an analogy of 
the most alluring and deceitful kind. Those who 
had seen heavy bodies revolving in the eddies of a 
whirlpool, or in the gyrations of a vessel of water 
thrown into a circular motion, had no difficulty in 
conceiving how the planets might revolve round the 
sun by analogous movements. The mind instantly 
grasped at an explanation of so palpable a character, 
and which required for its development neither the 
exercise of patient thought nor the aid of mathe- 
matical skill. The talent and perspicuity with which 
the Cartesian system was expounded, and the show 
of experiments with which it was sustained, con- 
tributed powerfully to its adoption, while it derived a 
still higher sanction from the excellent character 
and the unaffected piety of its author. 

Thus intrenched, as the Cartesian system was, in 
the strongholds of the human mind, and fortified by 
its most obstinate prejudices, it was not to be won- 
dered at that the pure and sublime doctrines of the 
Principia were distrustfully received and persever- 
ingly resisted. The uninstructed mind could not 
readily admit the idea, that the great masses of the 
planets were suspended in empty space, and retained 
in then orbits by an invisible influence residing in 
the sun ; and even those philosophers who had been 
accustomed to the rigour of true scientific research, 
and who possessed sufficient mathematical skill for 
the examination of the Newtonian doctrines, viewed 
them at first as reviving the occult qualities of the 
ancient physics, and resisted their introduction with 
a pertinacity which it is not easy to explain. Preju- 
diced, no doubt, in favour of his own metaphysical 
views, Leibnitz himself misapprehended the princi- 
ples of the Newtonian philosophy, and endeavoured 
to demonstrate the truths in the Principia by the appli- 
cation of different principles. Huygens, who above all 
other men was qualified to appreciate the new philo* 



NEWTONIAN PHILOSOPHY. 161 

sophy, rejected the doctrine of gravitation as existing 
? between the individual particles of matter, and re- 
; ceived it only as an attribute of the planetary masses, 
f John Bernouilli, one of the first mathematicians of 
j his age, opposed the philosophy of Newton. Mai- 
Iran, in the early part of his life, was a strenuous de- 
I fender of the system of vortices. Cassini and Ma- 
Iraldi were quite ignorant of the Principia, and occu- 
ipied themselves with the most absurd methods of 
I calculating the orbits of comets long after the New- 
I toman method had been established on the most 
I impregnable foundation ; and even Fontenelle, a man 
I of liberal views and extensive information, continued, 
I throughout the whole of his life, to maintain the 
I doctrines of Descartes. 

The Chevalier Louville of Paris had adopted the 
I Newtonian philosophy before 1720. S'Gravesande 
I had introduced it into the Dutch universities at a 
somewhat earlier period, and Maupertuis, in conse- 
quence of a visit which he paid to England in 1728, 
became a zealous defender of it; but notwithstand- 
ing these and some other examples that might be 
quoted, we must admit the truth of the remark of 
Voltaire, that though Newton survived the publica- 
tion of the Principia more than forty years, yet at 
the time of his death he had not above twenty fol- 
lowers out of England. 

With regard to the progress of the Newtonian 
philosophy in England, some difference of opinion 
has been entertained. Professor Playfair gives the 
following account of it. i; In the universities of 
England, though the Aristotelian physics had made 
an obstinate resistance, they had been supplanted 
by the Cartesian, which became firmly established 
about the time when their foundation began to be? 
sapped by the general progress of science, and par- 
ticularly by the discoveries of Newton. For more 
than thirty years after the publication of these dis- 
coveries, the system of vortices kept its ground; and 
02 



162 SIR ISAAC NEWTON. 

ia translation from the French into Latin of the 
sics of feohault, a work entirely Cartesian, con- 
tinued at Cambridge to be the text^-for philosophical 
instruction." About the year 1718,^ new and more 
elegant translation of the same book was published 
by Dr. Samuel Clarke, with the addition of notes, in 
which that profound and ingenious writer explained 
the views of Newton on the principal objects of 
discussion, so that the notes contained virtually a 
refutation of the text; they did so, however, only 
virtually, all appearance of argument and contro- 
versy being carefully avoided. Whether this escaped 
the notice of the learned doctor or not is uncertain, 
but the new translation, from its better Latinity, and 
the name of the editor, was readily admitted to all 
the academical honours which the old one had en- 
joyed. Thus the stratagem of Dr. Clarke com- 
pletely succeeded ; the tutor might prelect from the 
text, but the pupil would sometimes look into the 
notes ; and error is never so sure of being exposed 
as when the truth is placed close to it, side by side, 
without any thing to alarm prejudice, or awaken - 
from its lethargy the dread of innovation. Thus, 
therefore, the Newtonian philosophy first entered 
the university of Cambridge under the protection of 
the Cartesian." To this passage Professor Playfair 
adds the following as a note : 

" The universities of St. Andrew's and Edinburgh 
were, I believe, the first in Britain where the New- 
sman philosophy was made the subject of the aca- 
demical prelections. For this distinction they are 
Indebted to James and David Gregory, the first in 
$ome respects the rival, but both the friends of 
Newton. Whiston bewails, in the anguish of his 
heart, the difference, in this respect, between those 
universities and his own. David Gregory taught in 
Edinburgh for several years prior to 1690, when he 
removed to Oxford ; and Whiston says, ' He had 
already caused several of his scholars to keep acts,; 



NEWTONIAN PHILOSOPHY. 163 

as we call them, upon several branches of the New- 
Ionian philosophy, while we at Cambridge, poor 
I wretches, were ignominiously studying the fictitious 
| hypotheses of the Cartesians.'* I do not, however, 
i mean to say, that from this date the Cartesian phi- 
i losophy was expelled from those universities; the 
| Physics of Rohault were still in use as a text-book, 
I at least occasionally, to a much later period than this, 
L and a great deal, no vx^^bt, depended on the character 
I of the individual. Professor Keill introduced the 
\ Newtonian philosophy in his lectures at Oxford in 
; 1697 ; but the instructions of the tutors, which con- 
E stitute the real and efficient system of the univer- 
| sity, were not cast in that mould till long afterward." 
Adopting the same view of the subject, Mr. Dugald 
Stewart has stated, " that the philosophy of Newton 
was publicly taught by David Gregory at Edinburgh, 
and by his brother, James Gregory, at St. Andrew's,! 
before it was able to supplant the vortices of Des- 
cartes in that very university of which Newton 
was a member. It was in the Scottish universities 
that the philosophy of Locke, as well as that of 
Newton, was first adopted as a branch of academi- 
cal education." 

Anxious as we should have been to have awarded 
to Scotland the honour of having first adopted the 
Newtonian philosophy, yet a regard for historical 
truth compels us to take a different view of the sub- 
ject. It is well known that Sir Isaac Newton de- 
livered lectures on his own philosophy from the 
Lucasian chair before the publication of the Prin- 
cipia; and in the very page of Whiston's life quoted 
by Professor Playfair, he informs us that he had 
heard him read such lectures in the public schools, 



* Whiston's Memoirs of his own Life. 

f " Dr. Reid states, that James Gregory, Professor of Philosophy at 
St. Andrew's, printed a thesis at Edinburgh in 1690, containing twenty- 

ftvo nrsifinn<5 nf which t\*r3ntv_twA w*ir*> n /mnn*>fiH rf N>.wtnn's Prin 



cipia." 



164 SIR ISAAC NEWTON. 

though at that time he did not at all understand 
them. Newton continued to lecture till 1699, and 
occasionally, we presume, till 1703, when Whiston 
became his successor, having been appointed his 
deputy in 1699. In both of these capacities Wins- 
ton delivered in the public schools a course of lec- 
tures on astronomy, and a course of physico-mathe- 
matical lectures, in which the mathematical philoso- 
phy of Newton was explained and demonstrated, 
and both these courses were published, the one in 
1707, and the other in 1710, " for the use of the 
young men in the university." In 1707, the cele- 
brated blind mathematician Nicholas Saunderson 
took up his residence in Christ's College without 
being admitted a member of that body. The society 
not only allotted to him apartments, but gave him 
the free use of their library. With the concurrence 
of Whiston he delivered a course of lectures " on 
the Principia, Optics, and Universal Arithmetic of 
Newton," and the popularity of these lectures was 
so great, that Sir Isaac corresponded on the subject 
of -them with their author ; and on the ejection of 
Whiston from the Lucasian chair in 1711, Saunderson 
was appointed his successor. In this important office 
he continued to teach the Newtonian philosophy till 
the time of his death, which took place in 1739. 

But while the Newtonian philosophy was thus 
regularly taught in Cambridge, after the publication 
of the Principia, there were not wanting other exer- 
tions for accelerating its progress. About 1694, the 
celebrated Dr. Samuel Clarke, while an under-grad- 
uate, defended, in the public schools, a question taken 
from the Newtonian philosophy; and his translation 
of Rohault's Physics, which contains 'references in 
the notes to the Principia, and which was published 
in 1697 (and not in 1718, as stated by Professor 
Playfair), shows how early the Cartesian system 
was attacked by the disciples of Newton. The 
author of the Life of Saunderson informs us, that 



PROGRESS IN ENGLAND. 165 

>lic exercises or acts founded on every part of the 
fewtonian system were veiy common about 1707, 
and so general \vere such studies in the university, 
! that the Principia rose to four times its original 
price.* One of the most ardent votaries of the 
f- Newtonian philosophy was Dr. Laughton, who had 
t been tutor in Glare Hall from 1694, and it is probable 
Ithat during the whole, or at least a greater part, of 
[his tutorship he had inculcated the same doctrines. 
lln 1709-10, when he was proctor of that college, in- 
^ stead of appointing a moderator, he discharged the 
\ office himself, and devoted his most active exertions 
| to the promotion of mathematical knowledge. Pre- 
(vious to this, he had even published a paper of ques- 
tions on the Newtonian philosophy, which appear to 
have been used as theses for disputations ; and such 
was his ardour and learning that they powerfully 
contributed to the popularity of his college. Be- 
tween 1706 and 1716, the year of his death, the cele- 
brated Roger Cotes, the friend and disciple of New- 
ton, filled the Plumian chair of astronomy and ex- 
perimental philosophy at Cambridge. During this 
period he edited the second edition of the Principia, 
which he enriched with an admirable preface, and 
thus contributed, by his writings as well as by his 
lectures, to advance the philosophy of his master. 
About the same time, the learned Dr. Bentley, who 
first made known the philosophy of his friend to the 
readers of general literature, filled the high office of 
master of Trinity College, and could not fail to have 
exerted his utmost influence in propagating doctrines 
which he so greatly admired. Had any opposition 
been offered to the introduction of the true system 
of the universe, the talents and influence of these 
individuals would have immediately suppressed it; 
but no such opposition seems to have been made ; 

* Nichols's Literary Anecdotes> vol. iii. p. 322. Cotes states in hi 
preface to the second edition of the Principia, that copies of the first 
edition could only be obtained at an immense price. 



166 SIR ISAAC NEWTON. 

and though there may have been individuals at Cam- 
bridge ignorant of mathematical science, who ad- 
hered to the system of Descartes, and patronised 
the study of the Physics of Rohault, yet it is pro- 
bable that similar persons existed in the universities 
of Edinburgh and St. Andrew's ; and we cannot re- 
gard their adherence to error as disproving the gen- 
eral fact, that the philosophy of Newton was quickly 
introduced into all the universities of Great Britain. 
But while the mathematical principles of the New- 
tonian system were ably expounded in our seats of 
learning, its physical truths were generally studied, 
and were explained and communicated to the public 
by various lecturers on experimental philosophy. 
The celebrated Locke, who was incapable of under- 
standing the Prlncipia from his want of mathemati- 
cal knowledge, inquired ofjHuygens if all the mathe- 
matical propositions in that work were true. When 
he was assured that he might depend upon their cer- 
tainty, he took them for granted, and carefully ex- 
amined the reasonings and corollaries deduced from 
them. In this manner he acquired a knowledge of 
the physical truths in the Principia, and became a 
firm believer in the discoveries which it contained. 
In the same manner he studied the treatise on Op- 
tics, and made himself master of every part of it 
which was not mathematical.* From a manuscript 
of Sir Isaac Newton's, entitled " A demonstration 
that the planets, by their gravity towards the sun, 
may move in ellipses,! found among the papers of 
Mr. Locke, and published by Lord King," it would 
appear that he himself had been at considerable 
trouble in explaining to his friend that interesting 
; doctrine. Thissmanuscript is endorsed, " Mr. New- 
ton, March, 1689." It begins with three hypotheses 

* Preface to Desaguliers's Experimental Philosophy. Dr. Desaguliera 
states that he was told this anecdote several times by Sii Isaac Newtou 
himself. 

t The Life of John Locke, p. 209-215, Lond. 1829. 



PROGRESS IN ENGLAND. 






(the first two being the two laws of motion, and the 
third the parallelogram of motion), which introduce 
the proposition of the proportionality of the areas 
to the times in motions round an immoveable centre 
of attraction.* Three lemmas, containing properties 
of the ellipse, then prepare the reader for the cele- 
brated proposition, that when a body moves in an 
ellipse,! the attraction is reciprocally as the square 
of the distance of the body from the focus to which 
it is attracted. These propositions are demonstrated 
in a more popular manner than in the Principia, but 
there can be no doubt that, even in their present 
modified form, they were beyond the capacity of 
Mr. Locke. 

Dr. John Keill was the first person who publicly 
taught natural philosophy by experiments. Desa- 
guliers informs us that this author " laid down very 
simple propositions,which he proved by experiments, 
and from these he deduced others more compound, 
which he still confirmed by experiments, till he had 
instructed his auditors in the laws of motion, the 
principles of hydrostatics and optics, and some of 
the chief propositions of Sir Isaac Newton concern- 
ing light and colours. He began these courses in 
Oxford about the year 1704 or 1705, and in that way 
introduced the love of the Newtonian philosophy." 
When Dr. Keill left the university, Desaguliers be- 
gan to teach the Newtonian philosophy by experi- 
ments. He commenced his lectures at Harthall in 
Oxford, in 1710, and delivered more than a hundred 
and twenty courses ; and when he went to settle in 
London in 1713, he informs us that he found " the 
Newtonian philosophy generally received among 
persons of all ranks and professions, and even 
among the ladies by the help of experiments." 
Such were the steps by which the Newtonian phi- 
losophy was established in Great Britain. From 

* Principia, lib. i. prop. i. 



168 SIR ISAAC NEWTON. 

the time of* the publication of the Principia, its 
mathematical doctrines formed a regular part of aca- 
demical education; and before twenty years had 
elapsed, its physical truths were communicated to 
the public in popular lectures illustrated by experi- 
ments, and accommodated to the capacities of those 
who were not versed in mathematical knowledge. 
The Cartesian system, though it may have lingered 
for a while in the recesses of our universities, was 
soon overturned ; and long before his death, Newton 
enjoyed the high satisfaction of seeing his philoso- 
phy triumphant in his native land. 



CHAPTER XII. 

Doctrine cf Infinite Quantities Labours of Pappus Kepler Cavalert 
Roberval Fermat Wall is Newton discovers the Hmomial Theo- 
rem and the Doctrine of Fluxions in 1666 His Manuscript Work 
containing this Doctrine communicated to his Friends His Treatise 
on Fluxions His Mathematical Tracts His Universal Arithmetic 
His Methodus DifferentialisHis Geometria Analytica His Solu' 
tion of the Problems proposed by Bernouilli aud Leibnitz Account 
of the celebrated Dispute respecting the Invention of FtuxionsCom- 
mercium Epistolicum Report of the Royal Society -^General View 
of the Controversy. 

PREVIOUS to the time of Newton, the doctrine of 
infinite quantities had been the subject of profound 
study. The ancients made the first step in this 
curious inquiry by a rude though ingenious attempt 
to determine the area of curves. The method of 
exhaustions which was used for this purpose con- 
sisted in finding a given rectilineal area to which the 
inscribed and circumscribed polygonal figures con- 
tinually approached by increasing the number of 
their sides. This area was obviously the area 
of the curve, and in the case of the parabola it was 
found by Archimedes to be two-thirds of the area 



INFINITE QUANTITIES. 169 

ied by multiplying the ordinate by the abscissa, 
ough the synthetical demonstration of the re- 
ts was perfectly conclusive, yet the method itself 
was limited and imperfect. 

The celebrated Pappus of Alexandria followed 
Archimedes in the same inquiries ; and in his demon- 
stration of the property of the centre of gravity 
of a plane figure, by which we may determine the 
solid formed by its revolution, he has shadowed 
forth the discoveries of later times. 
In his curious tract on Stereometry, published in 
615, Kepler made some advances in the doctrine 
f infinitesimals. Prompted to the task by a dis- 
pute with the seller of some casks of wine, he 
studied the measurement of solids formed by the 
revolution of a curve round any line whatever. 
In solving some of the simplest of Jhese problems, 
he conceived a circle to be formed of an infinite 
number of triangles having all their vertices in the 
centre, and their infinitely small bases in the circum- 
ference of the circle, and by thus rendering familiar 
the idea of quantities infinitely great and infinitely 
small, he gave an impulse to this branch of mathe- 
matics. The failure of Kepler, too, in solving some 
of the more difficult of the problems which he him- 
self proposed roused the attention of geometers, 
and seems particularly to have attracted the notice 
of Cavaleri. 

This ingenious mathematician was born at Milan 
in 1598, and was Professor of Geometry at Bologna. 
In his method of Indivisibles, which was published 
in 1635, he considered a line as composed of an in- 
finite number of points, a surface of an infinite 
number of lines, and a solid of an infinite number 
of surfaces ; and he lays it down as an axiom that 
the infinite sums of such lines and surfaces have the 
same ratio when compared with the linear or super- 
ficial unit, as the surfaces and solids which are to 
be determined. As it is not true that an infinite 
P 



170 SIR ISAAC NEWTON. 

number of infinitely small points can make a Jin 
or an infinite number of infinitely small lines a sur- 
face, Pascal removed this verbal difficulty by con- 
sidering a line as composed of an infinite number 
of infinilely short lines, a surface as composed of 
an infinite number of infinitely narrow parallelo- 
grams, and a solid of an infinite number of infinitely 
thin solids. But, independent of this correction, 
the conclusions deduced by Cavaleri are rigorously 
true, and his method of ascertaining the ratios of 
areas and solids to one another, and the theorems 
which he deduced from it may be considered as 
forming an era in mathematics. 

By the application of this method, Roberval and 
Toricelli showed that the area of the cycloid is three 
times that of its generating circle, and the former 
extended the method of Cavaleri to the case where 
the powers of the terms of the arithmetical pro- 
gression to be summed were fractional. 

In applying the doctrine of infinitely small quanti- 
ties to determine the tangents of curves, and the 
maxima and minima of their ordinates, both Ro- 
berval and Fermat made a near approach to the 
invention of fluxions so near indeed that both 
Lagrange and Laplace* have pronounced the latter 
to be the true inventer of the differential calculus. 
Roberval supposed the poh t which describes a 
curve to be actuated by two motions, by the compo- 
sition of which it moves in the direction of a tan- 
gent; and had he possessed the method of fluxions, 
he could, in every case, have determined the rela- 
tive velocities of these motions, which depend on 
the nature of the curve, and consequently the 
direction of the tangent which he assumed to be in 
the diagonal of a parallelogram whose sides had the 

* " On pent regarder Fermat," says Lagrange, " comme le premier 
inventeur des nouveaux calculs ;" and Laplace observes, "II paraitque 
Fermat, le veritable inventeur du calcnl diflerentiel, Pait envisage comma 
un cas particulier d*j celui des di^*erences," &c. 



INFINITE QUANTITIES. 171 

same ratio as the velocities. But as he was able 
ito determine these velocities only in the conic sec- 
|tions, &c. his ingenious method had but few appli- 
cations. 

The labours of Peter Fermat, a counsellor of the 
parliament of Toulouse, approached still nearer to 
the fluxionary calculus. In his method of deter- 
mining the maxima and minima of the ordinates of 
curves, he substitutes x-\-e for the independent 
variable x in the function which is to become a 
.maximum, and as these two expressions should be 
equal when e becomes infinitely small or 0, he frees 
this equation from surds and radicals, and after di- 
viding the whole by e, e is made = 0, and the equation 
for the maximum is thus obtained. Upon a similar 
principle he founded his method of drawing tangents 
to curves. But though the methods thus used by 
Fermat are in principle the same with those which 
connect the theory of tangents and of maxima 
and minima with the analytical method of exhibit- 
ing the differential calculus, yet it is a singular ex- 
ample of national partiality to consider the inventer 
of these methods as the inventer of the method of, 
fluxions. 

" One might be led," says Mr. Herschel, " to sup- 
pose by Laplace's expression that the calculus of 
finite differences had then already assumed a sys- 
tematic form, and that Fermat had actually observed 
the relation between the two calculi, and derived 
the one from the other. The latter conclusion 
would scarcely be less correct than the former. No 
method can justly be regarded as bearing any anal- 
ogy to the differential calculus which does not lay 
down a system of rules (no matter on what consid- 
erations founded, by what names called, or by what 
extraneous matter enveloped) by means of which 
the second term of the development of any function 
of x-{-e in powers of e, can be correctly calculated, 
quae extendet se,' to use Newton's expression, 



172 SIR ISAAC NEWTON. 

* citra ullum molestum calculum in terminis surdis 
seque ac in integris procedens.' It would be strange 
to suppose Fermat or any other in possession of 
such a method before any single surd quantity had 
ever been developed in a series. But, in point of 
fact, his writings present no trace of the kind ; and 
this, though fatal to his claim, is allowed by both the 
geometers cited. Hear Lagrange's candid avowal. 

* II fait disparaitre dans cette equation,' that of the 
maximum between x and e, ' les radicaux et les frac- 
tions s'il y en a.' Laplace, too, declares that ' il sa- 
voit etendre son calcul aux fonctions irrationelles 
en se debarrassant des irrationalites par 1'elevation 
des radicaux aux puissances." This is at once giv- 
ing up the point in question. It is allowing une- 
quivocally that Fermat in these processes only took 
a circuitous route to avoid a difficulty which it is 
one of the most express objects of the differential 
calculus to face and surmount. The whole claim 
of the French geometer arises from a confusion (too 
often made) of the calculus and its applications, the 
means and the end, under the sweeping head of 

* nouveaux calculs' on the one hand, and an asser- 
tion somewhat too unqualified, advanced in the 
warmth and generality of a preface, on the other."* 

The discoveries of Fermat were improved and 
simplified by Hudde, Huygens, and Barrow ; and by 
the publication of the Arithmetic of Infinites by Dr. 
Wallis, Savilian professor of geometry at Oxford, 
mathematicians were conducted to the very entrance 
of a new and untrodden field of discovery. This 
distinguished author had effected the quadrature of 
all curves whose ordinates can be expressed by any 
direct integral powers ; and though he had extended 
his conclusions to the cases where the ordinates are 
xpressed by the inverse or fractional powers, yet 

* Art. Mathematics, in the Edinburgh Encyclopaedia, volume xiii. 
p. 365. 



ARITHMETIC OF INFINITES. 173 

ie failed in its application. Nicolas Mercator (Kauff- 
tian) surmounted the difficulty by which Wallis 
nad been baffled, by the continued division of the 
numerator by the denominator to infinity, and then 
applying Wallis's method to the resulting positive 
Bowers. In this way he obtained, in 1667, the first 
general quadrature of the hyperbola, and, at the 
ame time, gave the regular development of a func- 
ion in series. 

In order to obtain the quadrature of the circle, Dr. 
Vallis considered that if the equations of the curves 
f which he had given the quadrature were arranged 
i a series, beginning with the most simple, these 
reas would form another series. He saw also that 
tie equation of the circle was intermediate between 
he first and second terms of the first series, or 
etween the equation of a straight line and that of 
parabola, and hence he concluded, that by interpo- 
ating a term between the first and second term of 
be second series, he would obtain the area of the 
ircle. In pursuing this singularly beautiful thought, 
Dr. Wallis did not succeed in obtaining the indefinite 
quadrature of the circle, because he did not employ 
(general exponents; but he was led to express the 
entire area of the circle by a fraction, the numerator 
and denominator of which are each obtained by 
the continued multiplication of a certain series of 
numbers. 

Such was the state of this branch of mathematical 
science, when Newton, at an early age, directed to 
it the vigour of his mind. At the very beginning 
of his mathematical studies, when the works of Dr. 
Wallis fell into his hands, he was led to consider 
how he could interpolate the general values of the 
areas in the second series of that mathematician. 
With this view he investigated the arithmetical law 
of the coefficients of the series, and obtained a 
general method of interpolating, not only the series 
above referred to, but also other series. These 
P2 



174 SIR ISAAC NEWTON. 

were the first steps taken by Newton, and, as he 
himself informs us, they would have entirely escaped 
from his memory if he had not, a few weeks 
before,* found the notes which he made upon the 
subject. When he had obtained this method, it oc- 
curred to him that the very same process was appli- 
cable to the ordinates, and, by following out this 
idea, he discovered the general method of reducing 
radical quantities composed of several terms into 
infinite series, and was thus led to the discovery of 
the celebrated Binomial Theorem. He now neglected 
entirely his methods of interpolation, and employed 
that theorem alone as the easiest and most direct 
method for the quadratures of curves, and in the solu- 
tion of many questions which had not even been 
attempted by the most skilful mathematicians. 

After having applied the Binomial theorem to the 
rectification of curves, and to the determination of 
the surfaces and contents of solids, and the position 
of their centres of gravity, he discovered the general 
principle of deducing the areas of curves from the 
Vjyrdinate, by considering the area as a nascent quan- 
tity, increasing by continual fluxion in the propor- 
tion of the length of the ordinate, and supposing 
the abscissa to increase uniformly in proportion to 
the time. In imitation of Cavalerius, he called the 
momentary increment of a line a point, though it is 
not a geometrical point, but an infinitely short line ; 
and the momentary increment of an area or surface 
he called a line, though it is not a geometrical line, 
but an infinitely narrow surface. By thus regarding 
lines as generated by the motion of points, surfaces 
by the motions of lines, and solids by the motion of 
surfaces, and by considering that the ordinates, ab- 
scissae, &c. of curves thus formed, vary according 
to a regular law depending on the equation of the 

* These facts are mentioned in Newton's letter to Oldenburgh, Octo 
ber 24, 1676. 



DOCTRINE OF FLUXIONS. 173 

:urve. he deduces from this equation the velocities 
.vith which these quantities are generated ; and by 
;he rules of infinite series he obtains the ultimate 
/alue of the quantity required. To the velocities 
Sivith which every line or quantity is generated, 
LVevvton gave the name of Fluxions, and to the lines 
or quantities themselves that of Fluents. This 
nethod constitutes the doctrine of fluxions v^hich 
Newton had invented previous to 1666, when the 
Breaking out of the plague at Cambridge drove him 
Tom that city, and turned his attention to other 
subjects. 

But though Newton had not communicated this 
invention to any of his friends, he composed 
ilis treatise, entitled Analysis per equationes numero 
terminorum infinitas, in which the principle of fluxions 
and its numerous applications are clearly pointed 
out. In the month of June, 1669, he communicated 
his work to Dr. Barrow, who mentions it in a letter 
o Mr. Collins, dated the 20th June, 1669, as the pro- 
duction of a friend of his residing at Cambiidge, who 
possesses a fine genius for such inquiries. On the 
1st July, he transmitted the work to Collins; and 
laving received his approbation of it, he informs him 
;hat the name of the author of it was Newton, a 
ellow of his own college, and a young man who 
lad only two years before taken his degree of M.A. 
ollins 'took a copy of this treatise, and returned the 
original to Dr. Barrow ; and this copy having been 
bund among Collins's papers by his friend Mr. Wil- 
iam Jones, and compared with the original manu- 
cript Arrowed from Newton, it was published with 
he coHsent of Newton in 1711, nearly fifty years 
after it was written. 

Though the discoveries contained in this treatise 
were not at first given to the world, yet they were 
made generally known to mathematician, by the 
correspondence of Collins, who communicated them 
to James Gregory; to MM. Bertet and Vernon in 



176 SIR ISAAC NEWTON. 

France; to Slusius in Holland; to Borelli in Italy? 
and to Strode, Townsend, and Oldenburg, in letter* 
dated between 1669 and 1672. 

Hitherto the method of fluxions was known only 
to the friends of Newton and their correspondents ; 
but, in the first edition of the Principia, which ap- 
peared in 1687, he published, for the first time, the 
^ fundamental principle of the fluxionary calculus, in 
the second lemma of the second book. No infor- 
mation, however, is here given respecting the algo- 
rithm or notation of the calculus ; and it was not till 
1693-5[?] that it was communicated to the mathemat- 
ical world in the second volume of Dr. Wallis's works, 
which were published in that year. This informa- 
tion was extracted from two letters of Newton 
written in 1692. 

About the year 1672, Newton had undertaken to 
publish an edition of Kinckhuysen's Algebra, with 
notes and additions. He therefore drew up a trea- 
tise, entitled, A Method of Fluxions, which he pro- 
posed as an introduction to that work ; but the fear 
of being involved in disputes about this new dis- 
covery, or perhaps the wish to render it more com- 
plete, or to have the sole advantage of employing 
it in his physical researches, induced him to abandon 
this design. At a later period of his life he again 
resolved to give it to the world ; but it did not ap- 
pear till after his death, when it was translated into 
English, and published in 1736, with a commentary 
by Mr. John Colson, Professor of Mathematics in 
Cambridge.* 

To the first edition of Newton's Optics^g^hich 
appeared in 1704, there were added two mathematical 

* Dr. Pomberton informs us that he had prevailed upon Sir Isaac to 
publish this treatise during his lifetime, and that he had for this purpose 
examined all the calculations and prepared part of the figures. But as 
the latter part of the treatise had never been finished, Sir Isaac was 
about to let him have other papers to supply what was wanting, when 
his death put a stop to the plan.Preface to Pemberton's View qf Sir 
Isaac Newton's Philosophy 



DOCTRINF OF FLUXIONS. 177 

realises, entitled, Tractatus duo de speciebus et mag- 
ittudine figurarum curvilinearum, the one bearing the 
itle of Tractatus de Quadraiura Curvarum, and the 
)ther Enumeratio linjarum tertii ordinis. The first 
;ontains an explanation of the doctrine of fluxions, 
ind of its application to the quadrature of curves ; 
md the second a classification of seventy-two curves 
)f the third order, with an account of their proper- 
ies. The reason for publishing these two tracts in 
lis Optics (in the subsequent editions of which they 
ire omitted) is thus stated in the advertisement : 

In a letter written to M. Leibnitz in the year 1679, 
ind published by Dr. Wallis, I mentioned a method 
>y which I had found some general theorems about 
squaring curvilinear figures on comparing them with 
he conic sections, or other the simplest figures with 
vhich they might be compared. And some years 
igo I lent out a manuscript containing such theo- 
ems ; and having since met with some things copied 
>ut of it, I have on this occasion made it public, pre- 
ixing to it an introduction, and joining a scholium 
3oncerning that method. And I have joined with it 
mother small tract concerning the curvilineal figures 
the second kind, which was also written many 
fears ago, and made known to some friends, who 
lave solicited the making it public." 

In the year 1707, Mr. Whiston published the alge- 
)raical lectures which Newton had, during nine years, 
delivered at Cambridge, under the title of Arithmetica 
Universalis, sive de Compositions et Resolutions Arith- 
inetica Liber. We are not accurately informed how 
Mr. Whiston obtained pr osession of this work ; but 
it is stated by one of the editors of the English 
edition, that " Mr. Whiston thinking it a pity that so 
noble and useful a work should be doomed to a col- 
lege confinement, obtained leave to make it public." 
It was soon afterward translated into English by 
Mr. Ralphson ; and a second edition of it, with im- 
provements by the author, was published at London 



178 SIR ISAAC NEWTON. 

in 1712, by Dr. Maclim, secretary to the Royal 
ciety. With the view of stimulating mathematicians 
1o write annotations on this admirable work, the 
celebrated S'Gravesande published a tract, entitled, 
Specimen Commentarii in Arithmeticam Universalem ; 
and Maclaurin's Algebra seems to have been drawn 
up in consequence of this appeal. 

Among the mathematical works of Newton we 
must not omit to enumerate a small tract entitled, 
Methodus Differ entialis, which was published with 
his consent in 1711. It consists of six propositions,, 
which contain a method of drawing a parabolic curv^ 
through any given number of points, and which arer 
useful for constructing tables by the interpolation of; 
series, and for solving problems depending on the 
quadrature of curves. 

Another mathematical treatise of Newton's was 
published for the first time in 1779, in Dr. Horsley's 
edition of his works.* It is entitled, Artis Analytics 
Specimina, vel Geometria Analylica. In editing this 
work, which occupies about 130 quarto pages, Dr. 
Horsley used three manuscripts, one of which was 
in the handwriting of the author ; .another, written; 
in an unknown hand, was given by Mr. William: 
Jones to the Honourable Charles Cavendish ; and a 
third, copied from this by Mr. James Wilson, the 
.editor of Robins's works, was given to Dr. Horsley 
by Mr. John Nourse, bookseller to the king. Dr. 
Horsley has divided it into twelve chapters, which; 
treat of infinite series ; of the reduction of affected 
equations; of the specious resolution of equations; 
of the doctrine of fluxions; of maxima and minima; 
of drawing tangents to curves ; of the radius of cur* 
vature ; of the quadrature of curves ; of the area of 
curves which are comparable with the conic sec* 
tions ; of the construction of mechanical problems; 
and on finding the lengths of curves. 

* IsEci Newtoni Opera quae extant omnia, vol. i. p. 38S-519. 



SOLUTION OF PROBLEMS. 179 

In enumerating the mathematical works of our 
rathor, we must not overlook his solutions of the 
celebrated problems proposed by Bernouilli and 
Leibnitz. On the Kalends of January, 1697, John 
3ernouilli addressed a letter to the most distin- 
guished mathematicians in Europe,f challenging 
hem to solve the two following problems : 

1. To determine the curve line connecting two 
ven points which are at different distances from 

he horizon, and not in the same vertical line, along 
hich a body passing by its own gravity, and begin- 
ing to move at the upper point, shall descend to the 

ower point in the shortest time possible. 

2. To find a curve line of this property that the 
wo segments of a right line drawn from a given 
oint through the curve, being raised to any given 
ower, and taken together, may make every where 
tie same sum. 

On the day after he received these problems, 
Newton addressed to Mr. Charles Montague, the 
^resident of the Royal Society, a solution of them 
oth. He announced that the curve required in the 
rst problem must be a cycloid, and he gave a 
nethod of determining it. He solved also the 
econd problem, and he showed that by the same 
method other curves might be found which shall cut 
ff three or more segments having the like proper- 
es. Leibnitz, who was struck with the beauty of 
le problem, requested Bernouilli, who had allowed 
ix months for its solution, to extend the period to 
welve months. This delay was readily granted, 
olutions were obtained from Newton, Leibnitz, and 
Marquis de L'Hopital ; and although that of 
Newton was anonymous, yet Bernouilli recognised 

it his powerful mind, " tanquam? says he, " ex 
ngue leonem" as the lion is known by his claw. 

The last mathematical effort of our author was 

* " Acutissimis aui toto orbe florent Mathematicis." 



(180 SIR ISAAC NEWTON. 

made with his usual success, in solving a problem 
which Leibnitz proposed in 1716, in a letter to the 
Abbe Conti, " for the purpose, as he expressed it 
of feeling the pulse of the English analysts." The 
object of this problem was to determine the curve 
which should cut at right angles an infinity of curves 
of a given nature, but expressible by the same equa- 
tion. Newton received this problem about five 
o'clock in the afternoon, as he was returning from 
the Mint; and though the problem was extremely, 
difficult, and he himself much fatigued with business,* 
yet he finished the solution of it before he wenk 
to bed. 

Such is a brief account of the mathematical writ- 
ings of Sir Isaac Newton, not one of which were 
voluntarily communicated to the world by himself, 
The publication of his Universal Arithmetic is said 
to have been a breach of confidence on the part of 
Whiston ; and, however this may be, it was an un- 
finished work, never designed for the public. The 
publication of his Quadrature of Curves, and of hii, 
Enumeration of Curve Lines, was rendered neces* 
sary, in consequence of plagiarisms from the manu* 
scripts of them which he had lent to his friends, and 
the rest of his analytical writings did not appear till 
after his death. It is not easy to penetrate into the 
motives by which this great man was on these 
occasions actuated. If his object was to keep pos- 
session of his discoveries till he had brought them 
to a higher degree of perfection, we may approve of 
the propriety, though we cannot admire the prudence 
of such a step. If he wished to retain to himself 
his own methods, in order that he alone might have 
the advantage of them in prosecuting his physical 
inquiries, we cannot reconcile so selfish a measure 
with that openness and generosity of character 
which marked the whole of his life. If he withheld 
his labours from the world in order to avoid the dis~ 
putes and contentions to which they might give rise, 



HISTORY OF FLUXIONS. 181 

[opted the very worst method of securing his 
iquillity. That this was the leading motive under 
ch he acted, there is little reason to doubt. The 
arty delay in the publication of his method of. flux- 
ons, after the breaking out of the plague at Cam- 
Bridge, was probably owing to his not having com- 
peted the algorithm of that calculus ; but no apology 
:an be made for the imprudence of withholding it 
my longer from the public. Had he published this 
loble discovery even previous to 1673, when his 
preat rival had not even entered upon those studies 
tvhich led him to the same method, he would have 
>ecured to himself the undivided honour of the 
nvention, and Leibnitz could have aspired to no other 
ame but that of an improver of the doctrine of flux- 
ons. But he unfortunately acted otherwise. He 
Announced to his friends that he possessed a method 
}f great generality and power ; he communicated to 
hem a general account of its principles and applica- 
ions ; and the information which was thus conveyed 
lirected the attention of mathematicians to subjects 
o which they might not have otherwise applied their 
Dowers. In this way the discoveries which he had 
previously made were made subsequently by others ; 
and Leibnitz, in place of appearing in the theatre of 
cience as the disciple and the follower of Newton, 
tood forth with all the dignity of a rival ; and, by 
he early publication of his discoveries had nearly 
placed himself on the throne which Newton was 
destined to ascend. 

It would be inconsistent with the popular nature 
of a work like this, to enter into a detailed history 
of the dispute between Newton and Leibnitz re- 
specting the invention of fluxions. A brief and 
general account of it, however, is indispensable. 

In the beginning of 1673, Leibnitz came to London 

in the suite of the Duke of Hanover, and he became 

acquainted with the great men who then adorned 

the capital of England. Among these was Olden- 

Q 



182 SBR ISAAC NEWTON. 

burg, a countryman of his own, who was then sec- 
retary to the Royal Society. About the beginning 
of March, in the same year, Leibnitz went to Paris, 
where, with the assistance of Huygens, he devoted 
himself to the study of the higher geometry. In 
the month of July he renewed his correspondence 
with Oldenburg, and he communicated to him some of 
the discoveries which he had made relative to series, 
particularly the series for a circular arc in terms of 
the tangent. Oldenburg informed him in return of 
the discoveries on series which had been made by 
Newton and Gregory ; and in 1676 Newton commu- 
nicated to him, through Oldenburg, a letter of fifteeE 
closely printed quarto pages, containing many of his 
analytical discoveries, and stating that he possessed 
a general method of drawing tangents, which he 
thought it necessary to conceal in two sentences of 
transposed characters. In this letter neither the 
method of fluxions nor any of its principles are 
communicated ; but the superiority of the method 
over all others is so fully described, that Leibnitz 
could scarcely fail to discover that Newton pos- 
sessed that secret of which geometers had so long 
been in quest. 

Had Leibnitz at the time of receiving this Icttei 
been entirely ignorant of his own differential method, 
the information thus conveyed to him by Newton 
could not fail to stimulate his curiosity, and excite 
his mightiest efforts to obtain possession of so great 
a secret. That this new method was intimately 
connected with the subject of series was clearly in- 
dicated by Newton; and as Leibnitz was deeply 
versed in this branch of analysis, it is far from im- 
probable that a mind of such strength and acuteness 
might attain his object by direct investigation. That 
this was the case may be inferred from his letter to 
Oldenburg (to be communicated to Newton) of the 
21st June, 1677, where he mentions that he had for 
some time been in possession of a method of draw- 



HISTORY OF FLUXIONS. 183 

ng tangents more general than that of Slusius, 
lamely, by the differences of ordinates. He then 
Droceeds with the utmost frankness to explain this 
nethod, which was no other than th^. differential 
3alculus. He describes the algorithm which he had 
idopted, the formation of differential equations, and 
he application of the calculus to various geometrical 
and analytical questions. No answer seems to have 
:>een returned to this letter either by Newton or 
Oldenburg, and, with the exception of a short letter 
rom Leibnitz to Oldenburg, dated 12th July, 1677, 
10 further correspondence seems to have taken 
)lace. This, no doubt, arose from the death of Ol- 
denburg in the month of August, 1677,* when the 
wo rival geometers pursued their researches with 
ill the ardour which the greatness of the subject 
Was so well calculated to inspire. 

In the hands of Leibnitz the differential calculus 
nade rapid progress. In the Acta Eruditorum, which 
>vas published at Leipsic in November, 1684, he gave 
tie first account of it, describing its algorithm in the 
ame manner as he had done in his letter to Olden- 
urg, and pointing out its application to the drawing 
f tangents, and the determination of maxima and 
ninima. He makes a remote reference to the simi 
ar calculus of Newton, but lays no claim to the sole 
avention of the differential method. In the same 
vork for June, 1686, he resumes the subject ; and 
vhen Newton had not published a single word upon 

* Henry Oldenburg, whose name is so intimately associated with the 
history of Newton's discoveries, was born at Bremen, and was consul 
from that town to London during the usurpation of Cromwell. Having 
lost his office, and being compelled to seek the means of subsistence, he 
became tutor to an English nobleman, whom he accompanied to Oxford 
in 1656. During his residence in that city he became acquainted with 
the philosophers who established the Royal Society, and upon the death 
of William Crown, the first secretary, he was appointed in 1663, joint 
secretary along with Mr. Wilkins. He kept up an extensive correspond- 
ence with the philosophers of all nations, and he was the author of sev- 
eral papers in the Philosophical Transactions, and of some works which 
have not acquired much celebrity. He died at Charlton, near Greea 
wieh, in August, 1677. 



184 SIR ISAAC NEWTON. 

fluxions, and had not even made known his notation 
the differential calculus was making rapid advance: 
on the Continent, and in the hands of James anc 
John Bernouilli had proved the means of solving 
some of the most important and difficult problems. 
The silence of Newton was at last broken, and ir 
the second lemma of the second book of the Prin- 
cipia, he explained the fundamental principle of the 
fluxionary calculus. His explanation, which occu- 
pied only three pages, was terminated with the fol- 
lowing scholium: "In a correspondence which 
took place about ten years ago between that very 
skilful geometer, G. G. Leibnitz, and myself, I an- 
nounced to him that I possessed a method of deter- 
mining maxima and minima, of drawing tangents, 
and of performing similar operations which was 
equally applicable to rational and irrational quanti- 
ties, and concealed the same in transposed letters 
involving this sentence, (data equations quotcunque 
fluentes quantitates involvente^ fluxiones invenire et vice 
versa). This illustrious man replied that he also 
had fallen on a method of the same kind, and he 
communicated to me his method which scarcely 
differed from mine except in the notation [and in the 
idea of the generation of quantities."]* This cele- 
brated scholium, which is so often referred to in the 
present controversy, has, in our opinion, been much 
misapprehended. While M. Biot considers it as 
" eternalizing the rights of Leibnitz by recognising 
them in the Principia," Professor Playfair regards it 
as containing " a highly favourable opinion on the 
subject of the discoveries of Leibnitz." To us it 
appears to be nothing more than the simple state- 
ment of the fact, that the method communicated by 
Leibnitz was nearly the same as his own ; and this 
much he might have said, whether he believed that 
Leibnitz had seen the fluxionary calculus among the 

* These words in brackets are in the second edition, but not in the first. 



HISTORY OF FLUXIONS. 185 

>apers of Collins, or was the independent inventor 
>f his own. It is more than probable, indeed, that 
vhen Newton wrote this scholium he regarded 
bnitz as a second inventor ; but when he found 
hat Leibnitz and his friends had showed a willing- 
tess to believe, and had even ventured to throw out 
he suspicion, that he himself had borrowed the doc- 
jine of fluxions from the differential calculus, he 
eems to have altered the opinion which he had 
ormed of his rival, and to have been willing in his 
urn to retort the charge. 

This change of opinion was brought about by a 
eries of circumstances over which lie had no con- 
rol. M. Nicolas Fatio de Duillier, a Swiss mathe- 
natician, resident in London, communicated to the 
loyal Society, in 1699, a paper on the line of quick- 
st descent, which contains the following observa- 
ions : " Compelled by the evidence of facts, I hold 
Vewton to have been the first inventor of this cal- 
ulus, and the earliest by several years ; and whether 
^eibnitz, the second inventor, has borrowed any thing' 
rom the other, I would prefer to my own judgment 
hat of those who have seen the letters and other 
opies of the same manuscripts of Newton." This 
mprudent remark, which by no means amounts to a 
harge of plagiarism, for Leibnitz is actually desig- 
tated the second inventor, may be considered as 
howing that the English mathematicians had been 
herishing suspicions unfavourable to Leibnitz, and 
here can be no doubt that a feeling had long pre- 
vailed that this mathematician either had, or might 
lave seen, among the papers of Collins, the u Analy- 
is per Equationes, fyc.? which contained the prin- 
.iples of the fluxionary method. Leibnitz replied to 
he remark of Duillier with much good feeling. 
le appealed to the facts as exhibited in his corres- 
pondence with Oldenburg ; he referred to Newton's 
scholium as a testimony in his favour ; and, without 
disDuting or acknowledging the priority of Newton's 



186 SIR ISAAC NEWTON. 

claim, he asserted his own right to the invention of 
the differential calculus . Fatio transmitted a reply to 
the Leipsic Acts ; but the editor refused to insert it. 
The dispute, therefore, terminated, and the feelings 
of the contending parties continued for some time 
in a state of repose, though ready to break out on 
the slightest provocation. 

When Newton's Optics appeared in 1704, accom- 
panied by his Treatise on the Quadrature of Curves, 
and his enumeration of lines of the third order, the 
editor of the Leipsic Acts (whom Newton supposed 
to be Leibnitz himself) took occasion to review the 
first of these tracts. After giving an imperfect 
analysis of its contents, he compared the method 
of fluxions with the differential calculus, and, in a 
sentence of some ambiguity, he states that Newton 
employed fluxions in place of the differences of Leib- 
nitz, and made use of them in his Principia in the 
same manner as Honoratus Fabri, in his Synopsis 
of Geometry, had substituted progressive motion in 
place of the indivisibles of Cavaleri.* As Fabri, 
therefore, was not the inventor of the method 
which is here referred to, but borrowed it from Ca- 
valeri, and only changed the mode of its expression, 
there can be no doubt that the artful insinuation 
contained in the above passage was intended to con- 
vey the impression that Newton had stolen his me- 
thod of fluxions from Leibnitz. The indirect char- 
acter of this attack, in place of mitigating its severity, 
renders it doubly odious ; and we are persuaded that 
no candid reader can peruse the passage without a 
strong conviction that it justifies, in the fullest man- 

r * As this passage is of essential importance in this controversy, we 
shall give it in the original. " Pro dijferentiis igitur Leibnitianis D. 
Newtonus adhibet, semper que adhibuit^JluxioneSj quee sunt quam prox- 
ime ut fluentium augmenta, sequalibus temporis particulis quam mini- 
mis genita ; iisque tarn in suis Principiis Naturae Mathematicis, turn in 
aliis postea editis, elegantcr est usus ; quern admodum et Honoratus 
Fabrius in sua Synopsi Geometrica, motuumque progressus Cavalle- 
riancs methodo siibstituit." 



HISTORY OF FLUXIONS. 187 

aer, the indignant feelings which it excited among 
the English philosophers. If Leibnitz was the author 
of the review, or if he was in any way a party to it, 
he merited the full measure of rebuke which was 
dealt out to him by the friends of Newton, and de- 
served those severe reprisals which doubtless im- 
bittered the rest of his days. He who dared to ac- 
! cuse a man like Newton, or indeed any man holding 
a fair character in society, with the odious crime of 
; plagiarism, placed himself without the pale of the 
ordinary courtesies of life, and deserved to have 
f the same charge thrown back upon himself. The 
, man who conceives his fellow to be capable of such 
intellectual felony, avows the possibility of himself 
I committing it, and almost substantiates the weakest 
evidence of the worst accusers. 

Dr. Keill, as the representative of Newton's 
friends, could not brook this base attack upon his 
countryman. In a letter printed in the Philosophi- 
cal Transactions for 1708, he maintained that Newton 
was " beyond all doubt" the first inventor of fluxions. 
He referred for a direct proof of this to his letters 
published by Wallis ; and he asserted " that the same 
calculus was afterward published by Leibnitz, the 
name and the mode of notation being changed-." 
If the reader is disposed to consider this passage 
as retorting the charge of plagiarism upon Leibnitz, 
he will readily admit that the mode of, its expres- 
sion is neither so coarse nor so insidious as that 
which is used by the writer in the Leipsic Acts. 
In a letter to Hans Sloane, dated March, 1711, Leib- 
nitz complained to the Royal Society of the treat- 
ment he had received. He expressed his conviction 
that Keill had erred more from rashness of judgment 
than from any improper motive, and that he did not 
regard the accusation as a calumny; and he re- 
quested that the society would oblige Mr. Keill to 
disown publicly the injurious sense which his words 
might bear. When this letter was read to the 



188 IR ISAAC NEWTON. 

society, Keill justified himself to Sir Isaac Newton 
and the other members by showing them the ob- 
noxious review of the Quadrature of Curves in the 
Leipsic Acts. They all agreed in attaching the same 
injurious meaning to the passage which we formerly 
quoted, and authorized Keill to explain and defend 
his statement. He accordingly addressed a letter 
to Sir Hans Sloane, which was read at the society 
on the 24th May, 1711, and a copy of which was 
ordered to be sent to Leibnitz. In this letter, which 
is one of considerable length, he declares that he 
never meant to state that Leibnitz knew either the 
name of Newton's method or the form of notation, 
and that the real meaning of the passage was, " that 
Newton was the first inventor of fluxions or of the 
differential calculus, and that he had given, in two 
letters to Oldenburg, and which he had transmitted 
to Leibnitz, indications of it sufficiently intelligible 
to an acute mind, from which Leibnitz derived, or at 
least might derive, the principles of his calculus." 

The charge of plagiarism which Leibnitz thought 
was implied in the former letter of his antagonist 
is here greatly modified, if not altogether denied. 
Keill expresses only an opinion that the letter seen 
by Leibnitz contained intelligible indications of the 
fluxionary calculus. Even if this opinion were cor- 
rect, it is no proof that Leibnitz either saw these indi- 
cations or availed himself of them, or if he did per- 
ceive them, it might have been in consequence of his 
having previously been in possession of the differential 
calculus, or having enjoyed some distant view of it. 
Leibnitz should, therefore, have allowed the dispute 
to terminate here ; for no ingenuity on his part, and 
no additional facts, could affect an opinion which 
any other person as well as Keill was entitled to 
maintain. 

Leibnitz, however, took a different view of the 
subject, and wrote a letter to Sir Hans Sloane, 
dated December 19, 1711, which excited new feelings, 



HISTORY OF FLUXIONS. 189 

and involved him in new embarrassments. Insensi- 
ble to the mitigation which had been kindly impressed 
bpon the supposed charge against his honour, he 
jalleges that Keill had attacked his candour and sin- 
scerity more openly than before; that he acted 
(without any authority from Sir Isaac Newton, who 
jwas the party interested ; and that it was in vain 
to justify his proceedings by referring to the provo- 
cation in the Leipsic Acts, because in that journal 
\no injustice had been done to any party, but every one 
\had received what was his due. He branded Keill with 
Ithe odious appellation of an upstart, and one little 
acquainted with the circumstances of the case ;* he 
called upon the society to silence his vain and un- 
just clamours,! which, he believed, were disapproved 
by Newton himself, who was well acquainted with 

te facts, and who, he was persuaded, would will- 
ingly give his opinion on the matter. 

This unfortunate letter was doubtless the cause 
of all the rancour and controversy which so speedily 
followed, and it placed his antagonist in a new and a 
more favourable position. It may be correct, thougfr 
few will admit it, that Keill's second letter was more 
injurious than the first; but it was not true that 
Keill acted without the authority of Newton, be- 
muse KeilPs letter was approved of and trans- 
mitted by the Royal Society, of which Newton was 
the president, and therefore became the act of that 
body. The obnoxious part, however, of Leibnitz's 
letter consisted in his appropriating to himself the 
opinions of the reviewer in the Leipsic Acts, by 
declaring that, in a review which charged Newton 
with plagiarism, every person had got what was 
his due. The whole character of the controversy 
was now changed : Leibnitz places himself in the 



* Homine docto, ged novo, et parjim perito rerum ante actarum cog 
nitare. 
t Vanae et injustae vociferationes. 



190 SIR ISAAC NEWTON. 

position of the party who had first disturbed the 
tranquillity of science by maligning its most distin- 
guished ornament ; and the Royal Society was im- 
periously called upon to throw all the light they 
could upon a transaction which had exposed their 
venerable president to so false a charge. The so- 
ciety, too, had become a party to the question, by 
their approbation and transmission of Keill's second 
letter, and were on that account alone bound to vin- 
dicate the step which they had taken. 

When the letter of Leibnitz, therefore, was read, 
Keill appealed to the registers of the society for; 
the proofs of what he had advanced ; Sir Isaac also 
expressed his displeasure at the obnoxious passage 
in the Leipsic Review, and at the defence of it by 
Leibnitz, and he left it to the society to act as they 
thought proper. A committee was therefore ap- 
pointed on the 1 1th March, consisting of Dr. Arbuth- 
not, Mr. Hill, Dr. Halley, Mr. Jones, Mr. Machin, 
and Mr. Burnet, who were instructed to examine 
the ancient registers of the society, to inquire into 
the dispute, and to produce such documents as they 
should find, together with their own opinions on the 
subject. On the 24th April the committee produced 
the following report : 

" We have consulted the letters and letter-books 
in the custody of the Royal Society, and those 
found among the papers of Mr. John Collins, dated 
between the years 1669 and 1677, inclusive ; and 
showed them to such as knew and avouched the 
hands of Mr. Barrow, Mr. Collins, Mr. Oldenburg, 
and Mr. Leibnitz; and compared those of Mr. 
Gregory with one another, and with copies of some 
of them taken in the hand of Mr. Collins ; and have 
extracted from them what relates to the matter re- 
ferred to us ; all which extracts herewith delivered 
to you we believe to be genuine and authentic. And 
by these letters and papers we find, 

" I. Mr. Leibnitz was in London in the beginning 



REPORT OF THE ROYAL SOCIETY. 191 

of the year 1673; and went thence, in or about 
March, to Paris, where he kept a correspondence 
with Mr. Collins by means of Mr. Oldenburg, till 
about September, 1676, and then returned by London 
and Amsterdam to Hanover : and that Mr. Collina 
was very free in communicating to able mathema- 
ticians what he had received from Mr. Newton and 
Mr. Gregory. 

" II. That when Mr. Leibnitz was the first time in 
London, he contended for the invention of another 
differential method properly so called ; and, notwith- 
standing that he was shown by Dr. Pell that it was 
Newton's method, persisted in maintaining it to be 
his own invention, by reason that he had found it by 
himself without knowing what Newton had done 
before, and had much improved it. And we find no 
mention of his having any other differential method 
than Newton's before his letter of the 21st of June, 
1677, which was a year after a copy of Mr. Newton's 
letter of the 10th of December, 1672, had been sent 
to Paris to be communicated to him ; and above foui 
years after, Mr. Collins began to communicate that 
fetter to his correspondent; in which letter the 
method of fluxions was sufficiently described to any 
intelligent person. 

" III. That by Mr. Newton's letter of the 13th of 
June, 1676, it appears that he had the method of 
fluxions above five years before the writing of that 
letter. And by his Analysis per ^Equationes numero 
Terminorum Infinitas, communicated by Dr. Barrow 
to Mr. Collins in July, 1669, we find that he had in- 
vented the method before that time. 

" IV. That the differential method is one and the 
same with the method of fluxions, excepting the 
name and mode of notation ; Mr. Leibnitz calling 
those quantities differences which Mr. Newton calls 
moments or fluxions ; and marking them with the 
letter d a mark not used by Mr. Newton. 

" And therefore we take the proper question to be 



192 SIR ISAAC NEWTON. 

not who invented this or that method, but who was 
the first inventor of the method. And we believe 
that those who have reputed Mr. Leibnitz the first 
anventor knew little or nothing of his correspondence 
with Mr. Collins and Mr. Oldenburg long before, noi 
of Mr. Newton's having that method above fifteer 
Vears before Mr. Leibnitz began to publish it in the 
Acta Eruditorum of Leipsic. 

" For which reason we reckon Mr. Newton the 
first inventor ; and are of opinion that Mr. Keill, in 
asserting the same, has been no ways injurious to 
Mr. Leibnitz. And we submit to the judgment of 
the society whether the extract and papers now pre- 
sented to you, together with what is extant to the 
same purpose in Dr. Wallis's third volume, may not 
deserve to be made public." 

This report being read, the society unanimously 
ordered the collection of letters and manuscripts to 
be printed, and appointed Dr. Halley, Mr. Jones, and 
Mr. Machin to superintend the press. Complete 
copies of it, under the title of Commercium Epistoli- 
cwn D. Johannis Collins et aliorum de analyst promota, 
were laid before the society on the 8th January, 1713, 
and Sir Isaac Newton, as president, ordered a copy 
to be delivered to each person of the committee ap- 
pointed for that purpose, to examine it before its 
publication. 

Leibnitz received information of the appearance 
of the Commercium Epistolicum when he was at 
Vienna; and "being satisfied," as he expresses it, 
" that it must contain malicious falsehoods, I did not 
think proper to send for it by post, but wrote to M. 
Bernouilli to give me his sentiments. M. Bernoulli! 
wrote me a letter dated at Basle, June 7th, 1713, in 
which he said that it appeared probable that Sir Isaac 
Newton had formed his calculus after having seen 
mine"* This letter was published by a friend of 



* Letter to Count Bothman in Des Maizeaux's Recueil de diverse* 
vieces, torn ii, p. 41, 45. 



COMMERCIUM EPISTOLICUM. 193 

Leibnitz, with reflections, in a loose sheet entitled 
Charta Volans, and dated July 29, 1713. It was 
widely circulated without either the name of the 
author, printer, or place of publication, and was 
communicated to the Journal Literaire by another 
friend of Leibnitz, who added remarks of his own, 
and stated, that when Newton published the Principia 
in 1687, he did not understand the true differential 
method ; and that he took his fluxions from Leibnitz. 

In this state of the controversy, Mr. Chamberlayne 
conceived the design of reconciling the two distin- 
guished philosophers ; and in a letter dated April 28, 
1714,* he addressed himself to Leibnitz, who was 
still at Vienna. In replying to this letter, Leibnitz 
declared that he had given no occasion for the dis- 
pute ; " that Newton procured a book to be published, 
which was written purposely to discredit him, and 
sent it to Germany, &c. as in the name of the 
society ;" and he stated that there was room to doubt 
whether Newton knew his invention before he had it of 
him. Mr. Chamberlayne communicated this letter 
to Sir Isaac Newton, who replied that Leibnitz had 
attacked his reputation in 1705, by intimating that he 
had borrowed from him the method of fluxions ; 
that if Mr. C. could point out to him any thing in 
which he had injured Mr. Leibnitz, he would give 
him satisfaction ; that he would not retract things 
which he knew to be true ; and that he believed that 
the Royal Society had done no injustice by the publi- 
cation of the Commercium Epistolicum. 

The Royal Society, having learned that Leibnitz 
complained of their having condemned him unheard, 
inserted a declaration in their journals on the 20th 
May, 1714, that they did not pretend that the report 
of their committee should pass for a decision of the 
society. Mr. Chamberlayne sent a copy of this to 
Leibnitz, along with Sir Isaac's letter, and Dr. KeilTs 

* See Des Maizeaux, torn. ii. p. 116. 
R 



194 SIR ISAAC NEWTON. 

answer to 'the papers inserted in the Journal Lite- 
raire. After perusing these documents, M. Leibnitz 
replied, " that Sir Isaac's letter was written with 
very little civility; that he was not in a humour 
to put himself in a passion against such people; 
that there were other letters among those of Olden- 
burg and Collins which should have been published; 
and that on his return to Hanover, he would be able 
to publish a Commercium Epistolicum which would 
be of service to the history of learning." When 
this letter was read to the Royal Society, Sir Isaac 
remarked, that the last part of it injuriously accused 
the society of having made a partial selection of 
papers for the Commercium Epistolicum ; that he 
did not interfere in any way in the publication of 
that work, and had even withheld from the com- 
mittee two letters, one from Leibnitz in 1693, and 
another from Wallis in 1695, which were highly 
favourable to his cause. He stated that he did not 
think it right for M. Leibnitz himself, but that, if 
he had letters to produce in his favour, that they 
might be published in the Philosophical Transac- 
tions, or in Germany. 

About this time the Abbe Conti, a noble Vene- 
tian, came to England. He was a correspondent of 
Leibnitz, and in a letter which he had received soon 
after his arrival,* he enters upon his dispute with 
Newton. He charges the English "with wishing 
, to pass for almost the only inventors." He declares 
" that Bernouilli had judged rightly in saying that 
Newton did not possess before him the infinitesimal 
characteristic and algorithm." He remarks that 
Newton preceded him only in series; and he con- 
fesses that during his second visit to England, "Col- 
lins showed him part of his correspondence," or, as 
he afterward expresses it, he saw " some of the let- 
ters of Newton at Mr. Collins's." He then attacks 

* Written in November or December, 1715. 



COMMERCIUM EPISTOLICUM. 195 

Sir Isaac's philosophy, particularly his opinions 
about gravity and vacuum, the intervention of God 
for the preservation of his creatures ; and he accuses 
him of reviving the occult qualities of the schools. 
But the most remarkable passage in this letter is 
the following : " I am a great friend of experimental 
philosophy, but Newton deviates much from it when 
he pretends that all matter is heavy, or that each par- 
ticle of matter attracts every other particle." 

The above letter to the Abbe Conti was generally 
shown in London, and came to be much talked of at 
court, in consequence of Leibnitz having been privy 
counsellor to the Elector of Hanover when that 
prince ascended the throne of England. Many 
persons of distinction, and particularly the Abbe 
Conti, urged Newton to reply to Leibnitz's letter, 
but he resisted all their solicitations. One day, 
however, King George I. inquired when Sir Isaac 
Newton's answer to Leibnitz would appear; and 
when Sir Isaac heard this, he addressed a long reply 
to the Abbe Conti, dated February 26th, 0. S. 1715- 
16. This letter, written with dignified severity, is 
a triumphant refutation of the allegations of his ad- 
versary ; and the following passage deserves to be 
quoted, as connected with that branch of the dispute 
which relates to Leibnitz's having seen part of 
Newton's letters to Mr. Collins. " He complains 
of the committee of the Royal Society, as if they 
had acted partially in omitting what made* against 
me ; but he fails in proving the accusation. For he 
instances in a paragraph concerning my ignorance, 
pretending that they omitted it, and yet you will 
rind it in the Commercium Epistolicum, p. 547, lines 
2, 3, and I am not ashamed of it. He saith that he 
saw this paragraph in the hands of Mr. Collins when 
he was in London the second time, that is in Octo- 
ber, 1676. It is in my letter of the 24th of October, 
1676, and therefore he then saw that letter. And 



196 SIR ISAAC NEWTON. 

in that and some other letters writ before that time,' 
I described rny method of fluxions ; and in the same 
letter I described also two general methods of series, 
one of which is now claimed from me by Mr. Leib- 
nitz." The letter concludes with the following 
paragraph : " But as he has lately attacked me with 
an accusation which amounts to plagiary ; if he goes 
on to accuse me, it lies upon him by the laws of all 
nations to prove his accusations, on pain of being 
accounted guilty of calumny. He hath hitherto 
written letters to his correspondents full of affirma- 
tions, complaints, and reflections, without proving 
any thing. But he is the aggressor, and it lies upon 
him to prove the charge." 

In transmitting this letter to Leibnitz, the Abbe 
Conti informed him that he himself had read with 
great attention, and without the least prejudice, the 
Commercium Epistolicum, and the little piece* that 
contains the extract ; that he had also seen at the 
Royal Society the original papers of the Commer- 
cium Epistolicum, and some other original pieces 
relating to it. " From all this," says he, "I infer, 
that, if all the digressions are cut off, the only point 
is, whether Sir Isaac Newton had the method of 
fluxions or infinitesimals before you, or whether you 
had it before him. You published it first, it is true, 
but you have owned also that Sir Isaac Newton had 
given many hints of it in his letters to Mr. Olden- 
burg and others. This is proved very largely in the 
Commercium, and in the extract of it. What an- 
swer do you give ? This is still wanting to the 
public, in order to form an exact judgment of the 
affair." The Abbe adds, that Mr. Leibnitz's own 
friends waited for his answer with great impatience, 
and that they thought he could not dispense with 
answering, if not Dr. Keill, at least Sir Isaac New- 

* This is the Recensio Commercii Ipistolici, or review of it, which 
was first published in the Phil. Trans* 1715. 



GENERAL VIEW OF THE CONTROVERSY. 197 

ton himself, who had given him a defiance in express 
terms. 

Leibnitz was not long- in complying with this 
request. He addressed a letter to the Abbe Conti, 
dated April 9th, 1716, but he sent it through M. Ra- 
mond at Paris, to communicate it to others. When 
it was received by the Abbe Conti, Newton wrote 
observations upon it, which were communicated 
only to some of his friends, and which, while they 
placed his defence on the most impregnable basis, 
at the same time threw much light on the early his- 
tory of his mathematical discoveries. 

The death of Leibnitz on the 14th November, 
1716, put an end to this controversy, and Newton 
some time afterward published the correspondence 
with the Abbe Conti, which had hitherto been only 
privately circulated among the friends of the dispu- 
tants.* 

In 1722, a new edition of the Commercium Epis- 
tolicum was published, and there was prefixed to it 
a general review of its contents, which has been 
falsely ascribed to Newton. f When the third edi- 

* M. Biot remarks, that the animosity of Newton was not calmed by 
the death of Leibnitz, for he had no sooner heard of it than he caused to 
be printed two manuscript letters of Leibnitz, written in the preceding 
year, accompanying them with a very bitter refutation (en les accom- 
pagnant d'un refutation tres-amere). Who that reads this sentence 
does not believe that the bitter refutation was written after Leibnitz's 
death ? The animosity could not be shown by the simple publication 
of the letters. It could reside only in the bitterness of the refutation. 
The implied charge is untrue ; the bitter refutation was written before 
Leibnitz's death, and consequently he showed no animosity over the 
grave of his rival ; and in our opinion none even before his death. 

1 M. Biot states that Sir Isaac Newton caused this edition of the 
Commercium Epistolicum to be printed ; that Sir Isaac placed at the 
head of it a partial abstract of the collection ; and that this abstract 
appeared to have been written by himself These groundless charges 
may be placed, without any refutation, beside the assertion of Montucla, 
that Newton wrote the notes (les notes) on the Commercium Epis- 
tolicum ; and the equally incorrect statement of La Croix, that 
Newton added to it notes (des notes), with his own hand. We should 
not h-rve noticed the charges of M. Bior, had he not adduced them as 
proofs of Newton's animosity to Leibnitz after his death. See Mr. 
Herschel's H istory of Mathematics in the Edinburgh Encyclopedia^ 
ToL xiii. p. 368, note. 

R2 



198 SIR ISAAC NEWTON. 

tion of the Principia was published in 1725, the 
celebrated scholium which we have already quoted, 
and in which Leibnitz's differential calculus was 
mentioned, was struck out either by Newton or by 
the editor. This step was perhaps rash and ill- 
advised ; but as the scholium had been adduced by 
Leibnitz and others as a proof that Newton acknow- 
ledged him to be an independent inventor of the 
calculus, an interpretation which it does not bear, 
and which Newton expressly states he never in- 
tended it to bear, he was justified in withdrawing 
a passage which had been so erroneously inter- 
preted, and so greatly misapplied. 

In viewing this controversy, at the distance of 
more than a century, when the passions of the in- 
dividual combatants have been allayed, and national 
jealousies extinguished, it is not difficult to form a 
correct estimate of the conduct and claims of the 
two rival analysts. By the unanimous verdict of 
all nations, it has been decided that Newton invented 
fluxions at least ten years before Leibnitz. Some 
of the letters of Newton which bore reference to 
this great discovery were perused by the German 
mathematician ; but there is no evidence whatever 
that he borrowed his differential calculus from these 
letters. Newton was therefore the first inventor, 
and Leibnitz the second. It was impossible that the 
former could have been a plagiarist; but it was 
possible for the latter. Had the letters of Newton 
contained even stronger indications than they do of 
the new calculus, no evidence short of proof could 
have justified any allegation against Leibnitz's 
honour. The talents which he displayed in the im- 
provement of the calculus showed that he was 
capable of inventing it; and his character stood 
sufficiently high to repel every suspicion of his in- 
tegrity. But if it would have been criminal to 
charge Leibnitz with plagiarism, what must we 
think of those who dared to accuse Newton of bor 



GENERAL VIEW OF THE CONTROVERSY. 199 

I 

rowing his fluxions from Leibnitz? This odious 
accusation was made by Leibnitz himself, and by 
Bernouilli ; and we have seen that the former re- 
peated it again and again, as if his own good name 
rested on the destruction of that of his rival. It was 
this charge against Newton that gave rise to the at- 
tack of Keill, and the publication of the Commercium 
Epistolicum ; and, notwithstanding this high provo- 
cation, the committee of the Royal Society contented 
themselves with asserting Newton's priority, with- 
out retorting the charge of plagiarism upon his rival. 

Although an attempt has been recently made to 
place the conduct of Leibnitz on the same level with 
that of Newton, yet the circumstances of the case 
will by no means justify such a comparison. The 
conduct of Newton was at all times dignified and 
just. He knew his rights, and he boldly claimed 
them. Conscious of his integrity, he spurned with 
indignation the charge of plagiarism with which an 
ungenerous rival had so insidiously loaded him ; and 
if there was one step in his frank and unhesitating 
procedure which posterity can blame it is his omis- 
sion, in the third edition of the Principia, of the 
references to the differential calculus of Leibnitz. 
This omission, however, was perfectly^ just. The 
scholium which he had left out was a mere historical 
statement of the fact, that the German mathemati- 
cian had sent him a method which was the same as 
his own ; and when he found that this simple asser- 
tion had been held by Leibnitz and others as a re- 
cognition of his independent claim to the invention, 
he was bound either to omit it altogether, or to 
enter into explanations which might have involved 
him in a new controversy. 

The conduct of Leibnitz was not marked with the 
same noble lineaments. That he was the aggressor 
is universally allowed. That he first dared to 
breathe the charge of plagiarism against Newton, 
and that he often referred to it, has been sufficiently 



200 SIR ISAAC NEWTON. 

apparent; and when arguments failed him he had 
recourse to threats declaring that he would publish 
another Commercium Epistolicum, though he had 
no appropriate letters to produce. All this is now 
matter of hietory ; and we may find some apology 
for it in his excited feelings, and in the insinuations 
which were occasionally thrown out against the 
originality of his discovery.; but for other parts of 
his conduct we seek in vain for an excuse. When 
he assailed the philosophy of Newton in his letters 
to the Abbe Conti, he exhibited perhaps only the 
petty feelings of a rival ; but when he dared to ca- 
lumniate that great man in his correspondence with 
the Princess of Wales, by whom he was respected 
and beloved; when he ventured to represent the 
Newtonian philosophy as physically false, and as 
dangerous to religion ; and when he founded these 
accusations on passages in the Principia and the 
Optics glowing with all the fervour of genuine 
piety, he cast a blot upon his name, which all his 
talents as a philosopher, and all his virtues as a man, 
will never be able to efface. 



CHAPTER XIII. 

James IT. attacks the Privileges of the University of Cambridge New- 
Ion chosen one of the Delegates to resist this Encroachment He is 
elected a Member of the Convention Parliament Burning of his 
Manuscripts His supposed Derangement of Mind View taken of 
this by foreign Philosophers His Correspondence with Mr. Ptpys 
and Mr 1 Locke at the time of his Illness Mr. Millingtori's Letter to 
Mr. Pepys on the subject of Newton's Illness Refutation of the 
Statement that he laboured under Mental Derangement. 

FROM the year 1669, when Newton was installed 
in the Lucasian chair, till 1095, when he ceased to 
reside in Cambridge, he seems to have been seldom 
absent from his college more than three or four 



UNIVERSITY OF CAMBRIDGE. 201 

ireeks in the year. In 1675, he received a dispensa- 
tion from Charles II. to continue in his fellowship 
of Trinity College without taking orders, and we 
have already seen in the preceding chapter how his 
time was occupied till the publication of the Principia 
in 1687. 

An event now occurred which drew Newton from 
the seclusion of his studies, and placed him upon the 
theatre of public life. Desirous of re-establishing 
the Catholic faith in its former supremacy, King 
James II. had begun to assail the rights and privi- 
leges of his Protestant subjects. Among other illegal 
acts, he sent his letter of mandamus to the University 
of Cambridge to order Father Francis, an ignorant 
monk of the Benedictine order, to be received as 
master of arts, and to enjoy all the privileges of this 
degree, without taking the oaths of allegiance and 
supremacy. The university speedily perceived the 
consequences which might arise from such a meas- 
ure. Independent of the infringement of their rights 
which such an order involved, it was obvious that 
the highest interests of the university were endan- 
gered, and that Roman Catholics might soon become 
a majority in the convocation. They therefore 
unanimously refused to listen to the royal order, and 
they did this with a firmness of purpose which irri- 
tated the despotic court. The king reiterated his 
commands, and accompanied them with the severest 
threatenings in case of disobedience. The Catho- 
lics were not idle in supporting the views of the 
sovereign. The honorary degree of M.A. which 
conveys no civil rights to its possessor, having been 
formerly given to the secretary of the ambassador 
from Morocco, it was triumphantly urged that the 
University of Cambridge had a greater regard for a 
Mahometan than for a Roman Catholic, and was 
more obsequious to the ambassador from Morocco 
than to their own lawful sovereign. Though this 
reasoning might impose upon the ignorant, it pro- 



202 SIR ISAAC NEWTON. 

duced little effect upon the members of the univer- 
sity. A few weak-minded individuals, however, 
were disposed to yield a reluctant consent to the 
royal wishes. They proposed to confer the degree, 
and at the same time to resolve that it should not in 
future be regarded as a precedent. To this it was 
replied, that the very act of submission in one case 
would be a stronger argument for continuing the 
practice than any such resolution would be against 
its repetition. The university accordingly remained 
firm in their original decision. The vice-chancellor 
was summoned before the ecclesiastical commission 
to answer for this act of contempt. Newton was 
among the number of those who resisted the wishes 
of the court, and he was consequently chosen one 
of the nine delegates who were appointed to defend 
the independence of the university. These dele- 
gates appeared before the High Court. They main- 
tained that not a single precedent could be found to 
justify so extraordinary a measure ; and they showed 
that Charles II. had, under similar circumstances, 
been pleased to withdraw his mandamus. This 
representation had its full weight, and the king was 
induced to abandon his design.* 

The part which Newton had taken in this affair, 
and the high character which he now held in the 
scientific world, induced his friends to propose him 
as member of parliament for the university. He 
was accordingly elected in 1688, though by a very 
narrow majority,! and he sat in the Convention 
Parliament till its dissolution. In the year 1688 
and 1689, Newton was absent from Cambridge during 
the greater part of the year, owing, we presume, to 
his attendance in parliament; but it appears from 

* See Burnet's History of his own Times, vol. i. p. 697. Lond. 1724. 
1 The other candidates were Sir Robert Sawyer and Mr. Finch, ami 
the votes stood thus. 

Sir Robert Sawyer, 125 

Mr. Newton, 122 

Mr. Finch, 117 



BURNING OF HIS MANUSCRIPTS. 203 

lie books of the University that from 1690 to 1695 
le was seldom absent, and must therefore have 
renounced his parliamentary duties. 

During his stay in London he had no doubt expe- 
rienced the unsuitableness of his income to the new 
rircum stances in which he was placed, and it is 
probable that this was the cause of the limitation 
)f his residence to Cambridge. His income was 
certainly very confined, and but little suited to the 
generosity of his disposition. Demands were doubt- 
ess made upon it by some of his less wealthy rela- 
ives ; and there is reason to think that he himself, 
is well as his influential friends, had been looking 
"orward to some act of liberality on the part of the 
;overnment. 

An event however occurred which will ever form 
an epoch in his history ; and it is a singular circum- 
stance, that this incident has been for more than a 
century unknown to his own countrymen, and has 
>een accidentally brought to light by the examina- 
ion of the manuscripts of Huygens. This event 
has been magnified into a temporary aberration of 
nind, which is said to have arisen from a cause 
scarcely adequate to its production. 

While he was attending divine service in a winter 
norning, he had left in his study a favourite little 
dog called Diamond. Upon returning from chapel 
found that it had overturned a lighted taper on 
lis desk, which set fire to several papers on which 
he had recorded the results of some optical experi- 
ments. These papers are said to have contained the 
Labours of many years, and it has been stated that 
when Mr. Newton perceived the magnitude of his loss, 
be exclaimed, " Oh, Diamond, Diamond, little do you 
know the mischief you have done me !" It is a 
curious circumstance that Newton never refers to 
the experiments which he is said to have lost on this 
occasion, and his nephew, Mr. Conduit, makes no 
allusion to the event itself. The distress, however 



204 SIR ISAAC NEWTON. 

which it occasioned is said to have been so deep a 
to affect even the powers of his understanding. 

This extraordinary effect was first communicated 
to the world in the Life of Newton by M. Biot, who 
received the following account of it from the cele- 
brated M. Van Swinden. 

"There is among the manuscripts of the cele- 
brated Huygens a small journal in folio, in which 
he used to note down different occurrences. It is 
side No. 8, p. 112, in the catalogue of the library 
of Leyden. The following extract is written by 
Huygens himself, with whose handwriting I am well 
acquainted, having had occasion to peruse several 
of his manuscripts and autograph letters. ' On the 
29th May, 1694, M. Colin,* a Scotsman, informed me 
that eighteen months ago the illustrious geometer, Isaac 
Newton, had become insane, either in consequence of 
his too intense application to his studies, or from ex- 
cessive grief at having lost, by fire, his chymical labora- 
tory and several manuscripts. When he came to the 
Archbishop of Cambridge, he made some observations 
which indicated an alienation of mind. He was imme- 
diately taken care of by his friends, who confined him to 
his house and applied remedies, by means of which he 
had now so far recovered his health that he began to under- 
stand the PrincipiaS " Huygens mentioned this cir- 
cumstance to Leibnitz, in a letter dated 8th June. 
1694, to which Leibnitz replies in a letter dated the 
23d, " I am very glad that I received information of 
1 the cure of Mr. Newton, at the same time that I firsl 
heard of his illness, which doubtless must have beer 

* This M. Colin was probably a young bachelor of arts whom New 
ton seems afterward to have employed in some of his calculations 
These bachelors were distinguished by the title of Dominus, and it was 
usual to translate this word and to call them Sir. In a letter from New 
ton to Flamstead, dated Cambridge, June 29th, 1695, is the following 
passage : " I want not your calculations, but your observations only, for 
besides myself and my servant, Sir Collins (whom I can employ for f 
little money, which I value not) tells me that he can calculate "an eclipw 
and work truly. 



STATE OF HIS MIND. 205 

very alarming. ' It is to men like you and him, sir, 
that I wish a long life.' " 

The first publication of the preceding statement 
produced a strong sensation among the friends and 
admirers of Newton. They could not easily believe 
in the prostration of that intellectual strength which 
had unbarred the strongholds of the universe. The 
unbroken equanimity of Newton's mind, the purity 
of his moral character, his temperate and abstemious 
life, his ardent and unaffected piety, and the weak- 
ness of his imaginative powers, all indicated a mind 
which was not likely to be overset by any affliction 
to which it could be exposed. The loss of a few 
ixperimental records could never have disturbed the 
equilibrium of a mind like his. If they were the 
records of discoveries, the discoveries themselves 
ndestructible would have been afterward given to 
the world. If they were merely the details of ex- 
Derimental results, a little time could have easily 
'eproduced them. Had these records contained the 
irst fruits of early genius of obscure talent, on 
which fame had not yet shed its rays, we might have 
supposed that the first blight of such early ambition 
would have unsettled the stability of an untried 
mind. But Newton was satiated with fame. His 
mightiest discoveries were completed and diffused 
over all Europe, and he must have felt himself 
)laced on the loftiest pinnacle of earthly ambition. 
The incredulity which such views could not fail to 
encourage was increased by the novelty of the in. 
r ormation. No English biographer had ever alluded 
o such an event. History and tradition were equally 
silent, and it was not easy to believe that the Luca- 
sian Professor of Mathematics at Cambridge, a mem- 
ber of the English parliament, and the first philoso- 
pher in Europe could have lost his reason without 
the dreadful fact being known to his own countrymen. 

But if the friends of Newton were surprised by 
the nature of the intelligence, they w r ere distressed 
S 



206 SIR ISAAC NEWTON* 

at the view which was taken of it by foreign philoso- 
phers. While one maintained that the intellectual 
exertions of Newton had terminated with the publica- 
tion of the Principia, and that the derangement of 
his mind was the cause of his abandoning the sci- 
ences, others indirectly questioned the sincerity of 
his religious views, and ascribed to the aberration 
of his mind those theological pursuits which gilded 
his declining age. " But the fact," says M. Biot, 
" of the derangement of his intellect, whatever may 
have been the cause of it, will explain why, after the 
publication of the Principia in 1687, Newton, though 
only forty-five years old, never more published a 
new work on any branch of science, but contented 
himself with giving to the world those which he had 
composed long before that epoch, confining himself 
to the completion of those parts which might require 
development. We may also remark, that even 
these developments appear always to be derived 
from experiments and observations formerly made, 
such as the additions to the second edition of the 
Principia, published in 1713, the experiments on 
thick plates, those on diffraction, and the chymical 
queries placed at the end of the Optics in 1704 ; for 
in giving an account of these experiments Newton 
distinctly says that they were taken from ancient 
manuscripts which he had formerly composed ; and 
he adds, that though he felt the necessity of extend- 
ing them, or rendering them more perfect, he was 
not able to resolve to do this, these matters being no 
longer in his way. Thus it appears that though he 
had recovered his health sufficiently to understand 
all his researches, and even in some cases to make 
additions to them, and useful alterations, as appears 
from the second edition of the Principia, for which 
he kept up a very active mathematical correspond- 
ence with Mr. Cotes, yet he did not wish to under- 
take new labours in those departments t>f science 
where he had done so much, and where he so dis- 



STATE OF HIS MIND. 207 

tinctly saw what remained to be done." Under the 
influence of the same opinion, M. Biot finds " it ex- 
tremely probable that his dissertation on the scale 
of heat was written before the fire in his laboratory;" 
he describes Newton's conduct about the longitude 
bill as " almost puerile on so solemn an occasion, 
and one which might lead to the strangest conclu- 
sions, particularly if we refer it to the fatal accident 
which Newton had suffered in 1695." 

The celebrated Marquis de la Place viewed the 
illness of Newton in a light still more painful to his 
friends. He maintained that he never recovered the 
vigour of his intellect, and he was persuaded that 
Newton's theological inquiries did not commence 
till after that afflicting epoch of his life. He even 
commissioned Professor Gautier of Geneva to make 
inquiries on this subject during his visit to England, 
as if it concerned the interests of truth and justice 
to show that Newton became a Christian and a 
theological writer only after the decay of his 
strength and the eclipse of his reason. 

Such having been the consequences of the dis- 
closure of Newton's illness by the manuscript of 
Huygens, I felt it to be a sacred duty to the memory 
of that great man, to the feelings of his countrymen, 
and to the interests of Christianity itself, to inquire 
into the nature and history of that indisposition 
which seems to have been so much misrepresented 
and misapplied. From the ignorance of so extraor- 
dinary an event which has prevailed for such a long 
period in England, it might have been urged with 
some plausibility that Huygens had mistaken the 
real import of the information that was conveyed to 
him ; or that the Scotchman from whom he received 
it had propagated an idle and a groundless rumour. 
But we are, fortunately, not confined to this very 
reasonable mode of defence. There exists at Cam- 
bridge a manuscript journal written by Mr. Abraham 
de la Pryme, who was a student in the university 



208 SIR ISAAC NEWTON. 

while Newton was a fellow of Trinity. This manu- 
script is entitled " Ephemeris Vita, or Diary of my 
own Life, containing an account likewise of the most 
observable and remarkable things that I have taken 
notice of from my youth up hitherto." Mr. de la 
Pryme was born in 1671, and begins the diary in 
1685. This manuscript is in the possession of his 
collateral descendant, George Pryme, Esq., Profes- 
sor of Political Economy at Cambridge, to whom I 
have been indebted for the following extract. 

" 1692, February 3d. What I heard to-day I must 
relate. There is one Mr. Newton (whom I have 
very oft seen), Fellow of Trinity College, that is 
mighty famous for his learning, being a most excel- 
lent mathematician, philosopher, divine, &c. He 
has been Fellow of the Royal Society these many 
years; and among other very learned books and 
tracts, he's written one upon the mathematical prin- 
ciples of philosophy, which has got him a mighty 
name, he having received, especially from Scotland, 
abundance of congratulatory letters for the same ; 
but of all the books that he ever wrote, there was 
one of colours and light, established upon thousands 
of experiments which he had been twenty years of 
making, and which had cost him many hundred of 
pounds. This book, which he valued so much, and 
which was so much talked of, had the ill luck to 
perish and be utterly lost just when the learned 
author was almost at putting a conclusion at the 
same, after this manner: In a winter's morning, 
leaving it among his other papers on his study table 
while he went to chapel, the candle, which he had 
unfortunately left burning there too, catched hold 
by some means of other papers, and they fired the 
aforesaid book, and utterly consumed it and several 
other valuable writings ; and, which is most wonder- 
ful, did no further mischief. But when Mr. Newton 
came from chapel, and had seen what was done, 
every one thought he would have run mad, he wa 



STATE OF HIS MIND. 209 

50 troubled thereat that he was not himself for a 
nonth after. A long account of this his system of 
ight and colours you may find in the Transactions 
)f the Royal Society, which he had sent up to them 
ong before this sad mischance happened unto him." 
From this extract we are enabled to fix the ap- 
roximate date of the accident by which Newton 
ost his papers. It must have been previous to the 
d January, 1692, a month before the date of the 
xtract ; but if we fix it by the dates in Huygens's 
lanuscript, we should place it about the 29th No 
ember, 1692, eighteen months previous to the 
onversation between Collins and Huygens. The 
nanner in which Mr. Pryme refers to Newton's 
tate of mind is that which is used every day when 
ve speak of the loss of tranquillity which arises 
'om the ordinary afflictions of life ; and the meaning 
f the passage amounts to nothing more than that 
Newton was very much troubled by the destruction 
f his papers, and did not recover his serenity, and 
eturn to his usual occupations, for a month. The 
ery phrase that " every person thought he would 
ave run mad" is in itself a proof that no such effect 
as produced ; and, whatever degree of indisposi- 
pn may be implied in the phrase "he was not 
nimself for a month after," we are entitled to infer 
that one month was the period of its duration, and 
that previous to the 3d February, 1692, the date of Mr. 
Pryme's memorandum, "Newton was himself again." 
These facts and dates cannot be reconciled with 
those in Huygens's manuscript. It appears from 
that document, that, so late as May, 1694, Newton 
had only so far recovered his health as to begin 
to again understand the Principia. His supposed 
[malady, therefore, was in force from the 3d of 
! January, 1692, till the month of May, 1694, a 
iperiod of more than two years. Now, it is a most 
important circumstance, which M. Biot ought to 
have known, that in the very middle of this period, 
S3 



210 SIR ISAAC NEWTON. 

Newton wrote his four celebrated letters to Dr. 
Bentley on the Existence of a Deity, letters which 
evince a power of thought and a serenity of mind 
absolutely incompatible even with the slightest ob- 1 
scuration of his faculties. No man can peruse these 1 
letters without the conviction that their author their 
possessed the full vigour of his reason, and was< 
capable of understanding the most profound parts) 
of his writings. The first of these letters was writ-! 
ten on the 10th December, 1692, the second on thej 
17th January, 1693, the third on the 25th February! 
and the 4th on the llth* February, 1693. His mini 
was, therefore, strong and vigorous on these four) 
occasions; and as the letters were written at thej 
express request of Dr. Bentley, who had been ap-f 
pointed to deliver the lecture founded by Mr. Boylej 
for vindicating the fundamental principles of natural! 
and revealed religion, we must consider such a re-? 
quest as showing his opinion of the strength and 
freshness of his friend's mental powers. 

In 1692, Newton, at the request of Dr. Wallis, 
transmitted to him the first proposition of his book 
on quadratures, with examples of 'it in first, second, 
and third fluxions. f These examples were written 
in consequence of an application from his friend; 
and the author of the review of the Commercium 
Epistolicum, in which this fact is quoted, draws the 
conclusion, that he had not at that time forgotten 
his method of second fluxions. It appears, also, 
from the second book of the Optics,J that in the 
month of June, 1692, he had been occupied with the 
subject of haloes, and had made accurate observations 
both on the colours and the diameters of the rings 
in a halo which he had then seen around the sun. 

* They are thus dated in Horsley's edition of Newton's Works, the 
fourth letter having an earlier date than the third. 

t See Newtoni Opera, torn. iv. p. 480, and Wallasii Opera. 1693, torn. 
U. p. 391-396. 

; Optics, part iT. obs. 13. 



STATE OF HIS MIND. 211 

But though these facts stand in direct contradic- 
tion to the statement recorded by Huygens, the 
reader will be naturally anxious to know the real 
nature and extent of the indisposition to which it 
refers. The following letters,* written by Newton 
himself, Mr. Pepys, Secretary to the Admiralty, and 
Mr. Millington of Magdalene College, Cambridge, 
will throw much light upon the subject. 

Newton, as will be presently seen, had fallen into 
a bad state of health some time in 1692, in conse- 
quence of which both his sleep and his appetite 
were greatly affected. About the middle of Sep- 
tember, 1693, he had been kept awake for five nights 
by this nervous disorder, and in this condition he 
wrote the following letter to Mr. Pepys : 

" SIR, Sept. 13, 1693. 

" Some time after Mr. Millington had delivered 
your message, he pressed me to see you the next 
time I went to London. I was averse ; but upon 
his pressing consented, before I considered what I 
did, for I am extremely troubled at the embroilment 
I am in, and have neither ate nor slept well this 
twelvemonth, nor have my former consistency of 
mind. I never designed to get any thing by your 
interest, nor by King James's favour, but am now 
sensible that I must withdraw from your acquaint- 
ance, and see neither you nor the rest of my friends 
any more, if I may but leave them quietly. I beg 
your pardon for saying I would see you again, and 
rest your most humble and most obedient servant, 

" I. NEWTON." 

From this letter we learn, on his own authority, 
that his complaint had lasted for a twelvemonth, 
and that during that twelvemonth he neither ate nor 
slept well, nor enjoyed his former consistency of 

* For these letters I have been indebted to the kindness of Lord BrF- 
brooke. 



212 SIR ISAAC NEWTON 

mind. It is not easy to understand exactly what is 
meant by not enjoying his former consistency of 
mind ; but whatever be its import, it is obvious that 
he must have been in a state of mind so sound as to 
enable him to compose the four letters to Bentley, 
all of which were written during the twelvemonth 
here referred to. 

On the receipt of this letter, his friend Mr. Pepys 
seems to have written to Mr. Millington of Magda- 
lene College to inquire after Mr. Newton's health ; 
but the inquiry having been made in a vague man- 
ner, an answer equally vague was returned. Mr. 
Pepys, however, who seems to have been deeply 
anxious about Newton's health, addressed the fol- 
lowing more explicit letter to his friend Mr. Mil- 
lington : 

" SIR, Septemb. 26, 1693. 

"After acknowledging your many old favours, 
give me leave to do it a little more particularly upon 
occasion of the new one conveyed to me by my 
nephew Jackson. Though, at the same time, I 
must acknowledge myself not at the ease I would 
be glad to be at in reference to the excellent Mr. 
Newton ; concerning whom (methinks) your answer 
labours under the same kind of restraint which (to 
tell you the truth) my asking did. For I was loth 
at first dash to tell you that I had lately received a 
letter from him so surprising to me for the incon- 
sistency of every part of it, as to be put into great 
disorder by it, from the concernment I have for him, 
lest it should arise from that which of all mankind I 
should least dread from him and most lament for, I 
mean a discomposure in head, or mind, or both. Let 
me therefore beg you, sir, having now told you the true 
ground of the trouble I lately gave you, to let me 
know the very truth of the matter^ as far at least as 
comes within your knowledge. For I own too great 
an esteem for Mr. Newton, as for a public good, to 



STATE OF HIS MIND. 213 

1 >e able to let any doubt in me of this kind concern- 
ng him lie a moment uncleared, where I can have 
my hopes of helping it. I am, with great truth and 
respect, dear sir, your most humble, and most af- 
fectionate servant, 

" S. PEPYS." 

To this letter Mr. Millington made the following 
reply : 

Coll. Magd. Canib. 

" HONOR'D SIR, Sept. the 30, 1693. 

" Coming home from a journey on the 28th instant 
at night, I met with your letter which you were 
)leased to honour me with of the 26th. I am much 
troubled I was not at home in time for the post, 
that I might as soon as possible put you out of your 
generous payne that you are in for the worthy Mr 
Newton. I was, I must confess, very much surprised 
at the inquiry you were pleased to make by your 
Lephew about the message that Mr. Newton made 
-he ground of his letter to you, for I was very sure 
I never either received from you or delivered to him 
any such, and therefore I went immediately to wayt 
iipon him, with a design to discourse him about the 
(matter, but, he was out of town, and since I have 
not seen him, till upon the 28th I met him at Hunt- 
ingdon, where, upon his own accord, and before I 
had time to ask him any question, he told me that 
he had writt to you a very odd letter, at which he 
was much concerned ; added, that it was in a dis- 
temper that much seized his head, and that kept him 
awake for above five nights together, which upon 
occasion he desired I would represent to you, and 
beg your pardon, he being very much ashamed j he 
should be so rude to a person for whom he hath" so 
great an honour. He is now very well, and, though 
I fear he is under some small degree of melancholy, 
yet I think there is no reason to suspect it hath afr 



214 SIR ISAAC NEWTON. 

all touched his understanding, and I hope never will 
and so I am sure all ought to wish that love learning 
or the honour of our nation, which it is a sign hoi, 
much it is looked after, when such a person as Mr. New 
ton lyes so neglected by those in power. And thus, hon 
cured sir, I have made you acquainted with all '. 
know of the cause of such inconsistencys in th( 
letter of so excellent a person ; and I hope it wil 
remove the doubts and fears you are, with so mucl 
compassion and publickness of spirit, pleased tc 
entertain about Mr. Newton ; but if I should have, 
been wanting in any thing tending to the more fuL 
satisfaction, I shall, upon the least notice, endeav- 
our to amend it with all gratitude and truth. 
Honored sir, your most faithfull and most obedienl 
servant, 

"JOH. MlLLINGTON." 

Mr. Pepys was perfectly satisfied with this answer, 
as appears from the following letter : 

" SIR, October 3d, 1693. 

" You have delivered me from a fear that indeed 
gave me much trouble, and from my very heart I 
thank you for it ; an evil to Mr. Newton being what 
every good man must feel for his own sake as well 
as his. God grant it may stopp here. And for the 
kind reflection hee has since made upon his letter to 
mee, I dare not take upon mee to judge what an- 
swer I should make him to it, or whether any or no ; 
and therefore pray that you will bee pleased either 
to bestow on mee what directions you see fitt for 
my own guidance towards him in it, or to say to 
him in my name, but your own pleasure, whatever 
you think may be most welcome to him upon it, 
and most expressive of my regard and affectionate es- 
teem of him, and concernment for him. * 
* * * * Dear sir, your 
most humble and most faithful servant, 

" S. PEPYS," 



CORRESPONDENCE WITH LOCKE. 215 

It does not appear from the memoirs of Mr. 
Pepys whether he ever returned any answer to the 
etter of Mr. Newton which occasioned this corres- 
pondence ; but we find that in less than two months 
ifter the date of the preceding letter, an oppor- 
;unity occurred of introducing to him a Mr. Smith, 

o wished to have his opinion on some problem in 
he doctrine of chances. This letter from Pepys is 
Jated November 22d, 1693. Sir Isaac replied to it 
i>n the 26th November, and wrote to Pepys again 
the 16th December, 1693; and in both these 
etters he enters fully into the discussion of the 
nathematical question which had been submitted to 
lis judgment.* 

It is obvious, from Newton's letter to Mr. Pepys, 
hat the subject of his receiving some favour from 
he government had been a matter of anxiety with 
u'mself, and of discussion among his friends. f Mr. 
VTillington was no doubt referring to this anxiety, 
n he represents Newton as an honour to the 
lation, and expresses his surprise " that such a per- 
.on should lye so neglected by those in power" And 
ve find the same subject distinctly referred to in 
wo letters written to Mr. Locke during the pre- 
jeding year. In one of these, dated January 26th, 
691-2, he says, " Being fully convinced that Mr. 
VIontague, upon an old grudge which I thought had 
>een worn out, is false to me, I have done with him, 
,nd intend to sit still, unless my Lord Monmouth be 
till my friend." Mr. Locke seems to have assured 
lim of the continued friendship of this nobleman, 
md Mr. Newton, still referring to the same topic, 
n a letter dated February 16th, 1691-2, remarks, 



"* These three letters have been published by Lord Braybrooke in the 
,ife and Correspondence of Mr. Pepys. 

t This anxiety will be understood from the fact that, by an order of 
ouncil dated January 28th, 1674-5, Mr. Newton was excused from 
laking the usual payments of one shilling per week, " on account of Hia 
ow circumstances, as he represented." 



'216 SIR ISAAC NEWTON. 

I 

" I am very glad Lord Monmouth is still my friend, 
but intend not to give his lordship and you any far- 
ther trouble. My inclinations are to sit still." In 
a later letter to Mr. Locke, dated September, 1693, 
and given below, he asks his pardon for saying 01 
thinking that there was a design to sell him an 
office. In these letters Mr. Newton no doubt re- 
ferred to some appointment in London which he was 
solicitous to obtain, and which Mr. Montague and 
his other friends may have failed in procuring, 
This opinion is confirmed by the letter of Mr. Mon> 
tague announcing to him his appointment to the 
wardenship of the mint, in which he says that he is 
very glad he can at last give him good proof of his 
friendship. 

\ In the same month in which Newton wrote to Mr 
Pepys, we find him in correspondence with Mr 
Locke. Displeased with his opinions respecting 
innate ideas, he had rashly stated that they struct 
at the root of all morality ; and that he regardec 
the author of such doctrines as a Hobbist. Upor 
reconsidering these opinions, he addressed the fol- 
lowing remarkable letter to Locke, written three 
days after his letter to Mr. Pepys, and conse- 
quently during the illness under which he ther 
.laboured. 

" SIR, 

" Being of opinion that you endeavoured to em- 
broil me with women, and by other means, I was sc 
much affected with it, as that when one told me yot 
were sickly and would not live, I answered, 'twere 
better if you were dead. I desire you to forgive me 
this uncharitableness ; for I am now satisfied tha 1 
what you have done is just, and I beg your pardor 
for my having hard thoughts of you for it, and foi 
representing that you struck at the root of morality 



,in a principle you laid in your book of ideas, ari( 
{designed to pursue in another book, ; 



, and that I tool 



CORRESPONDENCE WITH LOCfcE. 217 

you for a Hobbist.* I beg your pardon also for 
saying or thinking that there was a design to sell me 
an office, or to embroil me. I am your most hum- 
ble and unfortunate servant, 

* " I s . NEWTON. 

" At the Bull, in Shoreditch, London, 
Sept. 16th, 1693." 

To this letter Locke returned the following an- 
swer, so nobly distinguished by philosophical mag- 
nanimity and Christian charity : 

" SIR, Oates, Oct. 5/A, 1693. 

" I have been, ever since I first knew you, so en 
tirely and sincerely your friend, and thought you so 
much mine, that I could not have believed what you 
tell me of yourself had I had it from anybody else. 
And, though I cannot but be mightily troubled that 
you should have had so many wrong and unjust 
thoughts of me, yet next to the return of good 
offices, such as from a sincere good-will I have ever 
done you, I receive your acknowledgment of the 
contrary as the kindest thing you have done me, 
since it gives me hopes I have not lost a friend I so 
much valued. After what your letter expresses, I 
shall not need to say any thing to justify myself to 
you. I shall always think your own reflection on 
my carriage, both to you and all mankind, will suffi- 
ciently do that. Instead of that, give me leave to 
assure you that I am more ready to forgive you than 
you can be to desire it ; and I do it so freely and fully, 
that I wish for nothing more than the opportunity 
to convince you that I truly love and esteem you, 
and that I have the same good-will for you as if 

* The system of Hobbes was at this time very prevalent. According 
to Dr. Bentley, " the taverns and coffee-houses, nay, Westminster Hall 
and the very churches, were full of it ;" and he was convinced from 
I personal observation, that " not one English infidel in a hundred was 
other than a Hobbist. " Monk\s Life of Bentley^ p. 31. 

T 



218 SIR ISAAC NEWTON. 

nothing of this had happened. To confirm this to 
you more fully, I should be glad to meet you any 
where, and the rather, because the conclusion of 
your letter makes me apprehend it would not be 
wholly useless to you. But whether you think it 
fit or not, I leave wholly to you. I shall always be 
ready to serve you to my utmost, in any way you 
shall like, and shall only need your commands or 
permission to do it. 

" My book is going to press for a second edition; 
and, though I can answer for the design with which, 
I write it, yet, since you have so opportunely given : 
me notice of what you have said of it, I should take 
it as a favour if you would point out to me the 
places that gave occasion to that censure, that, by 
explaining myself better, I may avoid being mis- 
taken by others, or unawares doing the least preju- 
dice to* truth or virtue. I am sure you are so much 
a friend to them both, that, were you none to me, I 
could expect this from you. But I cannot doubt but 
you would do a great deal more than this for my 
sake, who, after all, have all the concern of a friend 
for you, wish you extremely well, and am, without 
compliment, &c."* 



To this letter Newton made the following reply: 

" SIR, % 

" The last winter, by sleeping too often by my 
fire, I got an ill habit of sleeping ; and a distemper, 
which this summer has been epidemical, put me 
farther out of order, so that when I wrote to you, I 
had not slept an hour a night for a fortnight together, 
and for five days together not a wink. I remember 
I wrote to you, but what I said of your book I re- 
member not. If you please to send me a transcript 

* The draft of this letter is endorsed " J. L. to I. Newton." 



CORRESPONDENCE WITH LOCKE. 219. 

of that passage, I will give you an account of it if I 
can. I am your most humble servant, 

"I s - NEWTON. 
" Cambridge, Oct. Sth, 1693." 

Although the first of these letters evinces the 
existence of a nervous irritability which could not 
fail to arise from want of appetite and of rest, yet it 
is obvious that its author was in the full possession 
of his mental powers. The answer of Mr. Locke, 
indeed, is written upon that supposition ; and it de- 
serves to be remarked, that Mr. Dugald Stewart, 
who first published a portion of these letters, never 
imagines for a moment that Newton was labouring 
under any mental alienation. 

The opinion entertained by Laplace, that Newton 
devoted his attention to theology only in the latter 
Dart of his life, may be considered as deriving some 
countenance from the fact, that the celebrated gene- 
ral scholium at the end of the second edition of the 
Principia, published in 1713, did not appear in the 
irst edition of that work. This argument has been 
ably controverted by Dr. J. C. Gregory of Edinburgh, 
on the authority of a manuscript of Newton, which 
seems to have been transmitted to his ancestor, Dr. 
David Gregory, between the years 1687 and 1698. 
i This manuscript, which consists of twelve folio 
pages in Newton's handwriting, contains, in the 
form of additions and scholia to some propositions 
in the third book of the Principia, an account of the 
opinions of the ancient philosophers on gravitation 
and motion, and on natural theology, with various 
quotations from their works. Attached to this 
manuscript are three very curious paragraphs. The 
first two appear to have been the original draught 
of the general scholium already referred to ; and 
the third relates to the subject of an ethereal me- 
dium, respecting which he maintains an opinion 
diametrically opposite to that which he afterward 



220 SIR ISAAC NEWTON. 

published at the end of his Optics.* The first para- 
graph expresses nearly the same ideas as some 
sentences in the scholium beginning " Deus summus 
est ens asternum, infinitum, absolute perfectum ;"f 
and it is remarkable that the second paragraph is 
found only in the third edition of the Principia, 
which appeared in 1726, the year before Newton's 
death. 

In the middle of the year 1694, about the time 
when our author is said to be beginning to under- 
stand the Principia, we find him occupied with the 
difficult and profound subject of the lunar theory. 
In order to procure observations for verifying the 
equations which he had deduced from the theory of 
gravity, he paid a visit to Flamstead, at the Royal 
Observatory of Greenwich, on the 1st September, 
1694, when he received from him a series of lunar 
observations. On the 7th of October he wrote to 
Flamstead that he had compared the observations 
with his theory, and had satisfied himself that by 
both together " the moon's theory may be reduced 
to a good degree of exactness, perhaps to the exact- 
ness of two or three minutes." He wrote him again 
on the 24th October, and the correspondence was 
continued till 1698, Newton making constant appli- 
cation for observations to compare with his theory 

* Dr. Gregory concludes his account of this manuscript, which he has 
kindly permitted me to read, in the following words : " 1 do not know 
"whether it is true, as stated by Huygens, 4 Newtonurn incidisse in Phre- 
nitim ;' but I think every gentleman who examines this manuscript will 
be of opinion that he must have thoroughly recovered from his phrenitis 
before he wrote either the Commentary on the Opinions of the Ancients, 
or the Sketch of his own Theological and Philosophical Opinions which 
it contains." 

t This paragraph is as follows : " Deum esse ens summe perfectum 
concedunt omnes. Entis autem summe perfecti Idea est ut sit substan- 
tia, una, simplex, indivisibilis, viva et vivifica,ubique semper necessario 
existens, summe intelligens omnia, libere volens bona, voluntate efficiens 
possibilia, effectibus nobilioribus similitudinem propriam quantum fieri 
potest communicans, omnia in se continens tanquam eorurn principium. 
et locus, omnia per presentiam substantialem cernens et regens, et cum 
rebus omnibus, secundum leges accuratas ut naturae totius fundamen* 
turn et causa constanter co-operans, nisi ubi aliter agere bonum eat." 



CORRESPONDENCE WITH FLAMSTEAD. 221 

of the planetary motions ; while Flamstead, not suffi- 
ciently aware of the importance of the inquiry, re- 
ceived his requests as if they were idle intrusions in 
which the interests of science were but slightly con- 
cerned.* 

In reviewing the details which we have now given 
respecting the health and occupations of Newton 
from the beginning of 1692 till 1695, it is impossible 
to draw any other conclusion than that he possessed 
a sound mind, and was perfectly capable of carrying 
on his mathematical, his metaphysical, and his astro- 
nomical inquiries. His friend and admirer, Mr. 
Pepys, residing within fifty miles of Cambridge, had 
never heard of his being attacked with any illness 
till he inferred it from the letter to himself written 
in September, 1693. Mr. Millington, who lived in 
the same university, had been equally unacquainted 
with any such" attack, and, after a personal inter- 
view with Newton, for the express purpose of ascer- 
taining the state of his health, he assures Mr. Pepys 
" that he is very well, that he fears he is under 
some small degree of melancholy, but that there is 

* The following extract, characteristic of Flamstead's manner, is from 
a letter to Newton dated January 6, 1698-9. 

"Upon hearing occasionally that you had sent a letter to Dr. Wallis 
about the paraUax of the fixed stars to be printed, and that you had men- 
tioned me therein with respect to the theory of the moon, I was con- 
cerned to be publicly brought upon the state about what, perhaps, will 
never be fitted for the public, and thereby the world piit into an expecta 
tion of what perhaps they are never likely to have. I do not love to be 
printed upon every occasion, much less to be dunned and teased by 
foreigners about mathematical things, or to be thought by your own people 
to be trifling away my time when I should be about the king's business." 
On the first of the above passages in italics Flamstead has the follow- 
ing memorandum : " When Mr. Halley boasts 'tis done, and given to 
him as a secret, tells the Society so and foreigners.' In the second pas- 
sage in italics, Mr. Flamstead refers, in a note, to Mr. Colson's letter to 
him, in which he seems to have represented practical astronomy as 
trifling. Mr. Flamstead adds, " Was Mr. Newton a trifler when he read 
mathematics for a salary at Cambridge : surely, then, astronomy is of 
some good use, though his place be more beneficial." For these extracts 
from the original manuscript in the collection of Corpus Christi College, 
Oxford, I have been indebted to the kindness of Professor Rigaud of 
Oxford. 



222 SIR ISAAC NEWTON. 

no reason to suspect that it hath at all touched his 
understanding." 

During this period of bodily indisposition, his 
mind, though in a state of nervous irritability, and 
disturbed by want of rest, was capable of putting 
forth its highest powers. At the request of Dr. 
Wallis he drew up an example of one of his pro- 
positions on the quadrature of curves in second 
fluxions. He composed, at the desire of Dr. Bentley, 
his profound and beautiful letters on the existence 
of the Deity. He was requested by Locke to re- 
consider his opinions on the subject of innate ideas ; 
and we find him grappling with the difficulties of the 
lunar theory. 

But with all these proofs of a vigorous mind, a 
diminution of his mental powers has been rashly 
inferred from the cessation of his great discoveries, 
and from his unwillingness to enter upon new in- 
vestigations. The facts, however, here assumed 
are as incorrect as the inference which is drawn 
from them. The ambition of fame is a youthful 
passion, which is softened, if not subdued, by age. 
Success diminishes its ardour, and early pre-emi- 
nence often extinguishes it. Before the middle 
period of life Newton was invested with all the 
insignia of immortality ; but endowed with a native 
humility of mind, and animated with those hopes 
which teach us to form an humble estimate of human 
greatness, he was satisfied with the laurels which 
he had won, and he sought only to perfect and com- 
plete his labours. His mind was principally bent on 
the improvement of the Principia ; but he occasion- 
ally diverged into new fields of scientific research, 
he solved problems of great difficulty which had 
been proposed to try his strength, and he devoted 
much of his time to profound inquiries in chronology 
and in theological literature. 

The powers of his mind were therefore in full 
requisition; and, when we consider that he was 



MERITS NEGLECTED. 223 

called to the discharge of high official functions 
which forced him into public life, and compelled 
him to direct his genius into new channels, we can 
scarcely be surprised that he ceased to produce any 
original works on abstract science. In the direc- 
tion of the affairs of the mint, and of the Royal So- 
ciety, to which we shall now follow him, he found 
ample occupation for his time ; while the leisure of 
his declining years was devoted to those exalted 
studies in which philosophy yields to the supremacy 
of faith, and hope administers to the aspirations of 
genius. 



CHAPTER XIV. 

No Mark of National Gratitude conferred upon Newton Friendship 
between him and Charles Montague, afterward Earl of Halifax Mr 
Montague appointed Chancellor of the Exchequer in 1694 He resolves 
upon a Recoinage Nominates Mr. Newton Warden of the Mint in 
1695 Mr. Newton appointed Master of the Mint in 1699 Notice of 
the Earl of Halifax Mr. Newton elected Associate of the Academy 
of Sciences in 1699 Member for Cambridge in 1701 and President 
of the Royal Society in 1703 Queen Anne confers upon him the 
Honour of Knighthood in 1705 Second Edition of the Principia, 
edited by Cotes His Conduct respecting Mr. Ditton's Method of find- 
ing the Longitude. 

HITHERTO we have viewed Newton chiefly as a 
philosopher leading a life of seclusion within the 
walls of a college, and either engaged in the duties 
of his professorship, or ardently occupied in mathe- 
matical and scientific inquiries. He had now reached 
the fifty-third year of his age, and while those of his 
own standing at the university had been receiving 
high appointments in the church, or lucrative offices 
in the state, he still remained without any mark of 
the respect or gratitude of his country. All Europe 
indeed had been offering incense to his name, and 



224 SIR ISAAC NEWTON. 

Englishmen themselves boasted of him as the pride 
of their country and the ornament of their species, 
but he was left in comparative poverty,* with no 
other income than the salary of his professorship, 
eked out with the small rental of his paternal in- 
heritance. Such disregard of the highest genius, 
dignified by the highest virtue, could have taken 
place only in England, and we should have ascribed 
it to the turbulence of the age in which he lived, 
had we not seen, in the history of another century, 
that the successive governments which preside over 
the destinies of our country have never been able 
either to feel or to recognise the true nobility of 
genius. 

Among his friends at Cambridge Newton had the 
honour of numbering Charles Montague, grandson 
of Henry Earl of Manchester, a young man of high 
promise, and every way worthy of his friendship. 
Though devoted to literary pursuits, and twenty 
years younger than Newton, he cherished for the 
philosopher all the veneration of a disciple, and his 
affection for him gathered new strength as he rose 
to the highest honours and offices of the state. In 
the year 1684 we find him co-operating with Newton 
in the establishment of a philosophical society at 
Cambridge ; but though both of them had made per- 
sonal application to different individuals to become 
members, yet the plan failed, from the want, as 
Newton expresses it, of persons willing to try ex- 
periments. 

Mr. Montague sat along with Newton in the con- 
vention parliament, and such were the powers which 
he displayed in that assembly as a public speaker, 
that he was appointed a commissioner of the treasury, 
and soon afterward a privy counsellor. In these 
situations his talents and knowledge of business 
were highly conspicuous, and in 1694 he was ap 

* See page 215, note. 



WARDEN OF THE MINT. 225 

pointed chancellor of the exchequer. The current 
coin of the nation having been adulterated and de- 
based, one of his earliest designs was to recoin it 
and restore it to its intrinsic value. This scheme, 
however, met with great opposition. It was char- 
acterized as a wild project, unsuitable to a period 
of war, as highly injurious to the interests of com- 
merce, and as likely to sap the foundation of the 
government. But he had weighed the subject too 
deeply, and had intrenched himself behind opinions 
too impartial and too well-founded, to be driven from 
a measure which the best interests of his country 
seemed to require. 

The persons whom Mr. Montague had consulted 
about the recoinage were Newton, Locke, and Hal- 
ley, and in consequence of Mr. Overton, the warden 
of the mint, having been appointed a commissioner 
of customs, he embraced the opportunity which was 
thus offered of serving his friend and his country by 
recommending Newton to that important office. 
The notice of this appointment was conveyed in the 
following letter to Newton. 

" SIR, London, 19th March, 1695. 

" 1 am very glad that, at last, I can give you a 

food proof of my friendship, and the esteem the 
ing has of your merits. Mr. Overton, the warden 
of the mint, is made one of the commissioners of 
the customs, and the king has promised me to make 
Mr. Newton warden of the mint. The office is the 
most proper for you. 'Tis the chief office in the mint, 
'tis worth five or six hundred pounds per annum, and 
has not too much business to require more attendance 
than you can spare. T desire that you will come up 
as soon as you can, and I will take care of your 
warrant in the meantime. Let me see you as soon 
as you come to town, that I may carry you to kiss 
the king's hand. I believe you may have a lodging 
near me. I am, &c. CHARLES MONTAGUE*" 



226 SIR ISAAC NEWTON. 

In this new situation the mathematical and chy- 
mical knowledge of our author was of great service 
to the nation, and he became eminently useful in 
carrying on the recoinage, which was completed in 
the short space of two years. In the year 1699, he 
was promoted to the mastership of the mint, an 
office which was worth twelve or fifteen hundred 
pounds per annum, and which he held during the 
remainder of his life. In this situation he wrote an 
official report on the Coinage, which has been pub- 
lished ; and he drew up a table of Assays of Foreign 
Coins, which is printed at the end of Dr. Arbuthnot's 
Tables of Ancient Coins, Weights, and Measures, 
which appeared in 1727. 

While our author filled the inferior office of warden 
of the mint, he retained his professorship at Cam- 
bridge ; but upon his promotion in 1699, he appointed 
Mr. Whiston to be his deputy, with all the emolu- 
ments of the office ; and when he resigned the chair 
in 1703, he succeeded in getting him nominated his 
successor. 

The appointment of Newton to the mastership of 
the mint must have been peculiarly gratifying to 
the Royal Society, and it was probably from a feel- 
ing of gratitude to Mr. Montague, as much as from 
a regard for his talents, that this able statesman was 
elected president of that learned body on the 30th 
November, 1695. This office he held for three 
years, and on the 30th January, 1697, Newton had 
the satisfaction of addressing to him his solution of 
the celebrated problems proposed by John Bernouilli. 

This accomplished nobleman was created Earl of 
Halifax in 1700, and after the death of his first wife 
he conceived a strong attachment for Mrs. Catharine 
Barton, the widow of Colonel Barton, and the niece 
of Newton. This lady was young, gay, and beau- 
tiful, and though she did not escape the censures of 
her contemporaries, she was regarded by those who 
knew her as a woman of strict honour and virtue. 



PRESIDENT OF THE ROYAL SOCIETY. 227 

We are not acquainted with the causes which pre- 
vented her union with the Earl of Halifax, but so 
great was the esteem and affection which he bore 
her, that in the will in which he left 100/. to Mr. 
Newton, he bequeathed to his niece a very large 
portion of his fortune. This distinguished states- 
man died in 1715, in the fifty-fourth year of his age. 
Himself a poet and an elegant writer, he was the 
liberal patron of genius, and he numbered among 
his intimate friends Congreve, Halley, Prior, Tickell, 
Steele, and Pope. His conduct to Newton will be 
for ever remembered in the annals of science. The 
sages of every nation and of every age will pronounce 
with affection the name of Charles Montague, and 
the persecuted science of England will continue to 
deplore that he was the first and the last English 
minister who honoured genius by his friendship and 
rewarded it by his patronage. 

The elevation of Mr. Newton to the highest offices 
in the mint was followed by other marks of honour. 
The Royal Academy of Sciences at Paris having 
been empowered by a new charter granted in 1699, 
to admit a very small number of foreign associates, 
Newton was elected a member of that distinguished 
body. In the year 1701, on the assembling of a new 
parliament, he was re-elected one of the members 
for the University of Cambridge.* In 1703 he was 
chosen President of the Royal Society of London, 
anJ; he was annually re-elected to this office during 
the remaining twenty-five years of his life. On the 
16th of April, 1705, when Queen Anne was living at 
the royal residence of Newmarket, she went with 
Prince George of Denmark and the rest of the court 
to visit the University of Cambridge. After the 
meeting of the Regia Consilia, her majesty held a 

* The candidates in 1701 were as follows ; 
Mr. Henry Boyle, afterward Lord Carleton, 180 > Both of Trinity 

Mr. Newton 161 j College. 

Mr. Hammond .... 64 



228 SIR ISAAC NEWTON. 

court at Trinity Lodge, the residence of Dr. Bentley, 
then master of Trinity ; where the honour of knight- 
hood was conferred upon Mr. Newton, Mr. John Ellis, 
the vice-chancellor, and Mr. James Montague, the 
university counsel.* 

On the dissolution of the parliament, which took 
place in 1705, Sir Isaac was again a candidate for 
the representation of the University,^ but notwith- 
standing the recent expression of the* royal favour, 
he lost his election by .a very great majority.! 
This singular result was perhaps owing to the loss 
of that personal influence which his residence in the. 
university could not fail to command, though it is 
more probable that the ministry preferred the candi- 
dates of a more obsequious character, and that the 
electors looked for advantages which Sir Isaac New 
ton was not able to obtain for them. 

Although the first edition of the Principiahad been 
for some time sold off, and copies of it had become 
extremely rare, yet Sir Isaac's attention was so 
much occupied with his professional avocations that 
he could not find leisure for preparing a new edition. 
Dr. Bentley, who had repeatedly urged him to this 
task, at last succeeded, by engaging Roger Cotes, 
Plumian Professor of Astronomy at Cambridge, to 
superintend its publication at the university press. 
In June, 1709, Sir Isaac committed this important 
trust to his young friend ; and about the middle 1 of 
July he promised to send him in the course of a fort- 
night his own revised copy of the work. Business, 
however, seems to have intervened, and Mr. Cotes 
was obliged to remind Sir Isaac of his promise, which 
he did in the following letter : 

* The banquet which was on this occasion given in the college hall 
to the royal visiter seems to have cost about 1000Z., and the university 
was obliged to borrow 500/., to defray the expense of it.Monk'i Lift 
of Bentley, p. 143, 144. 
t The candidates in 1705 were as follows : 

The Hon. Arthur Annesley 182 
Hon. Dixie Windsor . 170 
Mr, Godolphin . . .162 
Sir Isaac Newton . . 117 



SECOND EDITION OF THE PRINCIPIA. 229 

" SIR, Cambridge, Aug. ISth, 1709. 

" The earnest desire I have to see a new edition 
f your Principia makes me somewhat impatient 
ill we receive your copy of it, which you were 
leased to promise me about the middle of last month 
r ou would send down in about a fortnight's time. 
3 hope you will pardon me for this uneasiness, from 
which I cannot free myself, and for giving you this 
;rouble to let you know it. I have been so much 
obliged by yourself and by your book, that (I desire 
you to believe me) I think myself bound in gratitude 
;o take all the care I possibly can that it shall be 
correct. Your obliged servant, 

" ROGER COTES. 

" For Sir Isaac Newton, at his house in 

Jermyn-street, near St. James's 

Church, Westminster." 

This was the first letter of that celebrated corres- 
>ondence, consisting of nearly three hundred letters, 
n which Sir Isaac and Mr. Cotes discussed the various 
mprovements which were thought necessary in a 
[lew edition of the Principia. This valuable collec- 
tion of letters is preserved in the library of Trinity 
College ; and we cannot refrain from repeating the 
wish expressed by Dr. Monk, " that one of the many 
accomplished Newtonians who are resident in that 
society would favour the world by publishing the 
whole collection." 

When the work was at last printed, Mr. Cotes ex- 
f >ressed a wish that Dr. Bentley should write the pre- 
face to it, but it was the opinion both of Sir Isaac 
and Dr. Bentley that the preface should come from 
|the pen of Mr. Cotes himself. This he accordingly 
undertook; but previous to its execution he ad- 
pressed the following letter to Dr. Bentley, in order 
to learn from Sir Isaac the particular view with 
which it should be written. 
U 



230 SIR ISAAC NEWTON. 

" SIR, March 10M, 1712-13. 

" I received what you wrote to me in Sir Isaac's 
letter. I will set about the index in a day or two. 
As for the preface, I should be glad to know from 
Sir Isaac with what view he thinks proper to have 
it written. You know the book has been received 
abroad with some disadvantage, and the cause of it 
may be easily guessed at. The Commercium Episto- 
licum, lately published by order of the Royal Society, 
gives such indubitable proofs of Mr. Leibnitz's want of 
candour, that I shall not scruple in the least to speak 
out the full truth of the matter, if it be thought 
convenient. There are some pieces of his looking 
this way which deserve a censure, as his Tentamen 
de motuum c&lestium causis. If Sir Isaac is willing 
that something of this nature may be done, I should 
be glad if, while I am making the index, he would 
consider of it, and put down a few notes of what he 
thinks most material to be insisted on. This I say 
upon supposition that I write the preface myself. 
But I think it will be much more advisable that you, 
or he, or both of you should write it while you are 
in town. You may depend upon it I will own it, 
and defend it as well as I can, if hereafter there be 
occasion. I am sir, &c." 

We are not acquainted with the instructions which 
were given to Mr. Cotes in consequence of this ap- 
plication; but it appears from the preface itself, 
which contains a long and able summary of the New- 
tonian philosophy, that Sir Isaac had prohibited any 
personal reference to the conduct of Leibnitz. 

The general preface is dated 12th May, 1713, and 
in a subsidiary preface of only a few lines, dated 
March 28th, i7I3, Sir Isaac mentions the leading 
alterations which had been made in this edition. 
The determination of the forces by which bodies 
may revolve in given orbits was simplified and en- 
larged. The theory of the resistance of fluids was 



LONGITUDE AT SEA. 231 

more accurately investigated, and confirmed by new 
experiments. The theory of the moon and the pre- 
cession of the equinoxes were more fully deduced 
from their principles ; and the theory of comets was 
confirmed by several examples of their orbits more 
accurately computed. 

In the year 1714, several captains and owners of 
merchant vessels petitioned the House of Commons 
to consider the propriety of bringing in a bill to 
reward inventions for promoting the discovery of 
the longitude at sea. A committee was appointed to 
investigate the subject, and Mr. Ditton and Mr. 
Whiston, having thought of a new method of finding 
the longitude, submitted it to the committee. Four 
members of the Royal Society, viz. Sir Isaac New- 
ton, Dr. Halley, Mr. Cotes, and Dr. Clarke, were 
examined on the subject, along with Mr. Ditton and 
Mr. Whiston. The last three of these philosophers 
stated their opinions verbally. Mr. Cotes considered 
the proposed scheme as correct in theory and on 
shore, and both he and Dr. Halley were of opinion 
that expensive experiments would be requisite. 
Newton, when called upon for his opinion, read the 
following memorandum, which deserves to be re- 
corded. 

" For determining the longitude at sea there have 
been several projects, true in theory, but difficult to 
execute. 

" 1. One is by a watch to keep time exactly; but 
by reason of the motion of the ship, the variation 
of heat and cold, wet or dry, and the difference of 
gravity in different latitudes, such a watch hath not 
yet been made. 

" 2. Another is by the eclipses of Jupiter's satel- 
lites; but by reason of the length of telescopes 
requisite to observe them, and the motion of a ship 
at sea, those eclipses cannot yet be there observed. 

" 3. A third is by the place of the moon ; but her 
theory is not yet exact enough for that purpose ; it 



232 SIR ISAAC NEWTON. 

is exact enough to determine the longitude within 
two or three degrees, but not within a degree. 

" 4. A fourth is Mr. Ditton's project, and this is 
rather for keeping an account of the longitude at 
sea than for rinding it, if at any time it should be 
lost, as it may easily be in cloudy weather. How far 
this is practicable, and with what charge, they that 
are skilled in sea affairs are best able to judge. In 
sailing by this method, whenever they are to pass 
over very deep seas, they must sail due east or west ; 
they must first sail into the latitude of the next place 
to which they are going beyond it, and then keep 
due east or west till they come at that place. In 
the first three ways there must be a watch regulated 
by a spring, and rectified every visible sunrise and 
sunset, to tell the hour of the day or night. In the 
fourth way such a watch is not necessary. In the 
first way there must be two watches, this and the 
other above mentioned. In any of the first three 
ways, it may be of some service to find the longitude 
within a degree, and of much more service to find it 
within forty minutes, or half a degree if it may, and 
the success may deserve rewards accordingly. In 
the fourth way, it is easier to enable seamen to 
know their distance and bearing from the shore 40, 
60, or 80 miles off, than to cross the seas ; and some 
part of the reward may be given when the first is 
performed on the coast of Great Britain for the safety 
of ships coming home ; and the rest when seamen 
shall be enabled to sail to an assigned remote har- 
bour without losing their longitude if it may be." 

The committee brought up their report on the llth 
June, and recommended that a bill should be intro- 
duced into parliament for the purpose of rewarding 
inventions or discoveries connected with the deter- 
mination of the longitude. The bill passed the 
House of Commons on the 3d July, and was agreed 
to by the Lords on the 8th of the same month.* 
* Journals of the House of Commons, voL xvii. p. 677, 716 



LONGITUDE AT SEA. 238 

In giving an account of this transaction,* Mr. 
Whiston states, that nobody understood Sir Isaac's 
paper, and that after sitting down he obstinately 
kept silence, though he was much pressed to explain 
himself more distinctly. At last, seeing that the 
scheme was likely to be rejected, Whiston ventured 
to say that Sir Isaac did not wish to explain more 
through fear of compromising himself, but that he 
really approved of the plan. Sir Isaac, he goes on 
to say, repeated word for word what Whiston had 
said. This is the part of Mr. Newton's conduct 
which M. Biot has described as puerile, and " tend- 
ing to confirm the fact of the aberration of his intel- 
lect in 1693." Before we can admit such a censure 
we must be satisfied with the correctness of Whis- 
km's statement. Newton's paper is perfectly intel- 
ligible, and we may easily understand how he might 
[lave approved of Mr. Ditton's plan as ingenious and 
practicable under particular circumstances, though 
he did not think it of that paramount importance 
which would have authorized the House of Com- 
mons to distinguish it by a parliamentary reward. 
The conflict between public duty and a disposition 
to promote the interests of Mr. Whiston and Mr. 
Ditton was no doubt the cause of that embarrass* 
ment of manner which the former of these mathe- 
maticians has so unkindly brought before the public. 

* Whiston's " Longitude Discovered." Lond 1738. 

us 



234 SIR ISAAC NEWTON. 



CHAPTER XV. 

Respect in which Newton was held at the Court of George L The Prtn* 
cess of Wales delighted with his Conversation Leibnitz et^.eavourtf 
to prejudice the Princess against Sir Isaac and Locker-Controversy 
occasioned by his Conduct The Princess obtains a Manuscript Ab 
stract of his System of Chronology The Abb4 Conti is, at her request, 
allowed to take a Copy of it on the promise of Secresy He prints it 
surreptitiously in French, accompanied with a Refutation by M. Freret 
-~Sir Isaac's Defence of his System Father Sonciet attacks it and 
ts answered by Dr. Halley~Sir Isaac's larger Work on Chronology 
published after his Death Opinions respecting it Sir Isaac's Paper 
on the Form of the most ancient Year. 

ON the accession of George I. to the British throne 
in 1714, Sir Isaac Newton became an object of in- 
terest at court. His high situation under govern- 
ment, his splendid reputation, his spotless charac- 
ter, and, above all, his unaffected piety attracted 
tfcs attention of the Princess of Wales, afterward 
queen-consort to George II. This lady, who pos- 
sessed a highly cultivated mind, derived" the greatest 
pleasure from conversing with Newton and corres- 
ponding with Leibnitz. In all her difficulties, she 
received from Sir Isaac that information and assist- 
ance which she had elsewhere sought in vain, and 
she was often heard to declare in public that she 
thought herself fortunate in living at a time which 
enabled her to enjoy the conversation of so great a 
genius. But while Newton was thus esteemed by 
the house of Hanover, Leibnitz, his great rival, en- 
deavoured to weaken and undermine his influence. 
In his correspondence with the princess, he repre- 
sented the Newtonian philosophy, not only as phy- 
sically false, but as injurious to the interests of 
religion. He asserted that natural religion was 
rapidly declining in England, and he supported this 
position by referring to the works of Locke, and to 



CHRONOLOGY. 235 

the beautiful and pious sentiments contained in the 
28th query at the end of the Optics. He represented 
;he principles of these great men as precisely the 
same with those of the materialists, and thus endea- 
oured to degrade the character of English philoso- 
phers. 

These attacks of Leibnitz became subjects of con- 
ersation at court, and when they reached the ear of 
he king, his majesty expressed his expectation that 
Sir Isaac Newton would draw up a reply. He ac- 
cordingly entered the lists on the mathematical part 
of the controversy, and left the philosophical part 
of it to Dr. Clarke, who was a full match for the 
jrerman philosopher. The correspondence which 
hus took place was carefully perused by the prin- 
cess, and from the estimation in which Sir Isaac 
Continued to be held, we may infer that the views of 
,he English philosopher were not very remote from 
ler own. 

When Sir Isaac was one day conversing with her 
oyal highness on some points of ancient history, 
le was led to mention to her, and to explain, a new 
system of chronology which he composed during his 
residence at Cambridge, where he was in the habit, 
as he himself expresses it, "of refreshing himself 
with history and chronology when he was weary 
with other studies." The princess was so much 
pleased with his ingenious system, that she subse- 
quently, in the year 1718, sent a message by the Abb6 
Conti to Sir Isaac, requesting him to speak with her, 
and she, on this occasion, requested a copy of the 
interesting work which contained his system of chro- 
nology. Sir Isaac informed her that it existed merely 
in separate papers, which were not only in a state 
of confusion, but which contained a very imperfect 
view of the subject, and he promised, in a few days, 
to draw up an abstract of it for her own private use, 
and on the condition that it should not be communi- 
cated to any other person. Some time after the 



236 sm ISAAC NEWTON. 

princess received the manuscript, she requested that 
the Abbe* Conti might be allowed to have a copy of 
it. Sir Isaac granted this request, and the Abbe was 
informed that he received a copy of the manuscript 
with Sir Isaac's leave, and at the princess's request, 
and that it was to be kept secret.* The manuscript 
which was thus rashly put into the hands of a 
foreigner was entitled " A Short Chronicle from the 
First Memory of Things in Europe to the Conquest 
of Persia by Alexander the Great." It consists of 
about twenty-four quarto printed pages,f with an 
introduction of four pages, in which Sir Isaac states 
that he " does not pretend to be exact to a year, that 
there may be errors of five or ten years, and some- 
times twenty, but not much above." 

The Abbe Conti kept his promise of secrecy during 
his residence in England, but he no sooner reached 
Paris than he communicated it to M. Freret, a 
learned antiquarian, who not only translated it, but 
drew up observations upon it for the purpose of re- 
futing some of its principal results. Sir Isaac was 
unacquainted with this transaction till he was in- 
formed of it by the French bookseller, M. Cavalier, 
who requested his leave to publish it, and charged 
one of his friends in London to procure Sir Isaac's 
answer, which was as follows : 

" I remember that I wrote a Chronological index 
for a particular friend, on condition that it should not 
be communicated. As I have not seen the manu- 
script which you have under my name, I know not 
whether it be the same. That which I wrote was 
not at all done with design to publish it. I intend 
not to meddle with that which hath been given you 

* This anecdote concerning the Chronological manuscript is not cor- 
rectly given in the Biographia Britannica, and in some of the other lives 
of Newton. I have followed implicitly Newton's own account of it in 
the Phil. Trans. 1725, vol. xxxiii. No. 389, p. 315. 

t M. Biot has supposed that this abstract was an imperfect edition of 
Newton's work on Chronology. 



CHRONOLOGY. 237 

T my name, nor to give any consent to the pub- 
ishing of it. I am your very humble servant, 

"ISAAC NEWTON. 
"London, May 21th, 1725, 0. S." 

Before this letter was written, viz. on the 21st 
May, the bookseller had received the royal privilege 
"or printing the work ; and when it was completed, 
le sent a copy in a present to Sir Isaac, who received 
t on the llth November, 1725. It was entitled, 
Abrege de Chronologie de M. Le Chevalier Newton, 
fait par lui-meme, et traduit sur le manuscript Anglais, 
tod was accompanied with observations by M. Fre- 
ret,* the object of which was to refute the leading 
points of the system.f An advertisement was pre- 
ixed to it, in which the bookseller defends himself 
"or printing it without the author's leave, on the 
round that he had written three letters to obtain 
)ermission, and had declared that he would take Sir 
isaac's silence for consent. When Sir Isaac received 
,his work, he drew up a paper entitled, Remarks on 
'he Observations made on a Chronological Index of Sir 
Isaac Newton, translated into French by the Observator, 
md published at Paris, which was printed in the Phi- 
losophical Transactions for 1725.J In this paper Sir 
[saac gives a history of the transaction,- charges 
,he Abbe Conti with a breach of promise, and blames 
;he publisher for having asked his leave to print the 
;ranslation without sending him a copy for his peru- 
sal, without acquainting him with the name of the 
translator, and without announcing his intention of 
printing along with it a refutation of the original. 

Father Souciet was supposed by Halley and others to have been the 
authorof these observations, but there is no doubt that they were written 
by M. Freret. 

f It is stated in the Biogr. Britannica, Art. Newton, that the copy of 
the French translation was not accompanied with the refutation. Though 
the reverse of this is not distinctly stated by Sir Isaac himself, yet it 
may be inferred from his observations. 

% Vol. xxxiii. No. 389, p. 315. 



238 SIR ISAAC NEWTON. 

The observations made by the translator against the 
conclusions deduced by the author were founded on 
an imperfect knowledge of Sir Isaac's system ; and 
they are so specious, that Halley himself confesses 
that he was at first prejudiced in favour of the obser- 
vations, taking the calculations for granted, and not 
having seen Sir Isaac's work. 

To all the observations of M. Freret Sir Isaac re- 
turned a triumphant answer. This presumptuous 
antiquary had ventured to state at the end of his 
observations, " that he believed he had stated enough 
concerning the epochs of the Argonauts, and the 
length of generations, to make people cautious about 
the rest; for these are the two foundations of all this 
new system of chronology." He founds his argu- 
ments against the epochs of the Argonauts, as fixed 
by our author, on the supposition that Sir Isaac 
places the vernal equinox at the time of the Argo- 
nautic expedition in the middle of the sign of Ariesj 
whereas Sir Isaac places it in the middle of the con- 
stellation, a point corresponding with the middle of 
the back of Aries, or 8 from the first star of Aries. 
This position of the colure is assigned on the author- 
ity of Eudoxus, as given by Hipparchus, who says 
that the colure passed over the back of Aries. Set- 
ting out with this mistake, M. Freret concludes that 
the Argonautic expedition took place 532 years 
earlier than Sir Isaac made it. His second objection 
to the new system relates to the length of genera 
tipns, which he says is made only 18 or 20 years. 
Sir Isaac, on the contrary, reckons a generation at 
33 years, or 3 generations at 100 ; and it was the 
lengths of the reigns of kings that he made 18 or 20 
years. This deduction he founds on the reigns of 
64 French kings. Now, the ancient Greeks and 
Egyptians reckoned the length of a reign equal to 
that of a generation ; and it was by correcting this 
mistake, and adopting a measure founded on fact, 
that Sir Isaac placed the Argonautic expedition forty- 



CHRONOLOGY. 239 

bur years after the^death of Solomon, and fixed some 
>f the other points' of his system. 

This answer of Sir Isaac's to the objections of 
<Yeret called into the field a fresh antagonist, Father 
Souciet, who published five dissertations on the new 
chronology. These dissertations were written in 

tone highly reprehensible ; and the friends of Sir 
'saac, being apprehensive that the manner in which 
lis system was attacked would affect him more than 
he arguments themselves, prevailed upon a friend to 
raw up an abstract of Souciet's objections, stripped 
>f the " extraordinary ornaments with which they 
*vere clothed." The perusal of these objections had 
10 other effect upon him than to convince him of 
;he ignorance of their author ; and he was induced 
:o read the entire work, which produced no change 
n his opinion. 

In consequence of these discussions, Sir Isaac 
was prevailed upon to prepare his larger work for 
;he press. v He had nearly completed it at the time 
)f his death, and it was published in 1728, under the 
itleof The Chronology of Ancient Kingdoms amended, 
o which is prefixed a short Chronicle, from the first 
memory of Things in Europe to the Conquest of Per- 
ia by Alexander the Great. It was dedicated to the 
jueen by Mr. Conduit, and consists of six chapters : 

On the Chronology of the Greeks ;* 2. Of the 
Empire of Egypt ; 3. Of the Assyrian Empire ; 4. 
)f the two contemporary Empires of the Baby- 
onians and Medes ; 5. A Description of the Temple 
)f Solomon; 6. Of the Empire of the Persians. 
The sixth chapter was not copied out with the other 
ive, which makes it doubtful whether or not it was 
ntended for publication ; but as it was found among 
lis papers, and appeared to be a continuation of the 

' According to Whiston, Sir Isaac wrote out eighteen copies of thta 
hapter with 'his own hand, differing little from one another Whi* 
on'vLife, p. 39. 



240 SIR ISAAC NEWTON. 

same work, it was thought right to add it to the 
other five chapters.* 

After the death of Newton, Dr. Halley, who had 
not yet seen the larger work, felt himself called upon, 
both as astronomer-royal and as the friend of the 
author, to reply to the first and last dissertations of 
Father Souciet, which were chiefly astronomical; 
and in two papers printed in the Philosophical Trans- 
actions for 1727,f he has done this in a most con- 
vincing and learned argument. 

\ Among the supporters of the views of Newton, . 
we may enumerate Dr. Reid, Nauze, and some other- 
writers ; and among its opponents, M. Freret, who 
left behind him a posthumous work on the subject, 
M. Fourmond, Mr. A. Bedford, Dr. Shuckford, Dr. 
Middleton, Whiston, and the late M. Delambre. The 
object of M. Fourmond is to show the uncertainty 
of the astronomical argument, arising on the one 
hand from the vague account of the ancient sphere 
as given by Hipparchus ; and, on the other, from the 
extreme rudeness of ancient astronomical observa- 
tions. Delambre has taken a similar view of the 
subject : he regards the observations of ancient 
astronomers as too incorrect to form the basis of a 
system of chronology ; and he maintains, that if we 
admit the accuracy of the details in the sphere of 
Eudoxus, and suppose them all to belong to the 
.same epoch, all the stars which it contains ought at 
that epoch to be found in the place where they are 
marked, and we might thence verify the accuracy, 
and ascertain the state of the observations. It fol- 
lows, however, from such an examination, that the 

* This work is the first article in the fifth volume of Dr. Horsley's 
edition of Newton's works. The next article in the volume is entitled, 
" A Short Chronicle from a MS., the property of the Reverend Dr. 
Ekins, Dean of Carlisle;" which is nothing more than the abstract of 
the Chronology already printed in the same volume. We cannot even 
conjecture the reasons for publishing it, especially as it is less perfect 
than the abstract, two or three dates being wanting. 

t See vol. xxxiv. p. 205, and vol. xxxv. p. 296 



CHRONOLOGY. 241 

; sphere would indicate almost as many different 
.epochs as it contains stars. Some of them even 
had not, in the time of Eudoxus, arrived at the po- 
sition which had been for a long time attributed to 
them, and will not even reach it for three hundred 
years to come, and on this account he considers it 
impossible to deduce any chronological conclusions 
from such a rude mass of errors. 

But however well-founded these observations may 

, we agree in opinion with M. Daunou,* "that 
they are not sufficient to establish a new system, 
and we must regard the system of Newton as a 
great fact in the history of chronological science, 
and as confirming the observation of Varro, that the 
stage of history does not commence till the first 
Olympiad." 

Among the chronological writings of Sir Isaac 
Newton we must enumerate his letter to a person 
of distinction who had desired his opinion of the learned 
Bishop Lloyd^s hypothesis concerning the form of the 
most ancient year. This hypothesis was sent by the 
Bishop of Worcester to Dr. Prideaux. Sir Isaac 
remarks, that it is filled with many excellent obser- 
vations on the ancient year ; but he does not " find 
"t proved that any ancient nations used a year of 
twelve months and 360 days without correcting it 

m time to time by the luminaries, to make the 
months keep to the course of the moon, and the year 
to the course of the sun, and returns of the seasons 
and fruits of the earth." After examining the years 
of all the nations of antiquity, he concludes, " that no 
other years are to be met with among the ancients 
3ut such as were either luni-solar, or solar or lunar, 
or the calendars of these years." A practical year, 
tie adds, of 360 days is none of these. The begin- 
ning of such a year would have run round the four 

* See an excellent view of this chronological controversy in an able 
note by M. Daunou, attached to Biot's Life of Newton in the Biog. Uni 
verselle t tom - xxxi. p. 180 

A. 



242 SIR ISAAC NEWTON. 

seasons in seventy years, and such a notable revolu- 
tion would have been mentioned in history, and is 
not to be asserted without proving it.* 



CHAPTER XVI. 

Theological Studies of Sir Isaac Their Importance to Christianity 
Motives to which they have been ascribed Opinions of Biot and La- ' 
place considered His Theological Researches begun before his sup* 
posed Mental Illness The Date of these Works fixed Letters to Locke 
Account of his Observations on Prophecy- -His Historical Account 
of two notable Corruptions of Scripture His Lexicon Propheticum 
His Four Letters to Dr. Bentley Origin of Newton's Theological 
Studies Analogy between the Book of Nature and that of Revelation 

THE history of the theological studies of Sir Isaac 
Newton will ever be regarded as one of the most 
interesting portions of his life. That he who among 
all the individuals of his species possessed the high- 
est intellectual powers was not only a learned and , 
profound divine, but a firm believer in the great doc- 
trines of religion, is one of the proudest triumphs 
of the Christian faith. Had he distinguished him- 
self only by an external respect for the offices and 
duties of religion ; and had he left merely in his last 
words an acknowledgment of his faith, his piety 
would have been regarded as a prudent submission 
to popular feeling, and his last aspirations would 
have been ascribed to the decay or to the extinction 
of his transcendent powers. But he had been a 
Christian from his youth, and though never intended 
for the church, yet he interchanged the study of the 
Scriptures with that of the laws of the material 
universe ; and from the examination of the works 
of the Supreme Creator- he found it to be no abrupt 

* This letter is published without any date in the Gentleman's Maga- 
zine for 1755^vol. xxv. p. 3. It bears internal evidence of being genuine 



THEOLOGICAL STUDIES. 243 

transition to investigate the revelation of his will, 
fand to contemplate the immortal destinies of man- 
[kind. 

But when the religious habits of Sir Isaac Newton 
[could not be ascribed to an ambiti6n of popularity, 
to the influence of weak health, or to the force of 
[professional impulse, it became necessary for the 
apostles of infidelity to refer it to some extraordi- 
nary cause. His supposed insanity was therefore 
eagerly seized upon by some as affording a plausible 
origin for his religious principles ; while others, 
without any view of supporting the cause of skep- 
ticism, ascribed his theological researches to the 
habits of the age in which he lived, and to a desire 
of promoting political liberty, by turning against the 
abetters of despotism those powerful weapons which 
the Scriptures supplied. The anxiety evinced by 
M. de Laplace to refer his religious writings to a 
late period of his life seems to have been felt also 
by M. Biot, who has gone so far as to fix the very 
date of one of his most important works, and thus 
to establish the suspicions of his colleague. 

' From the nature of the subject,"* says he, " and 
from certain indications which Newton seems to 
give at the beginning of his dissertation, we may 
conjecture with probability that he composed it at 
the time when the errors of Whiston, and a work 
of Dr. Clarke on the same subject, drew upon them 
the attacks of all the theologians of England, which 
would place the date between the years 1712 and 
1719. It would then be truly a prodigy to remark, 
that a man of from seventy-two to seventy-five 
years of age was able to compose, rapidly, as he 
leads us to believe, so extensive a piece of sacred 
criticism, of literary history, and even of bibliogra- 
phy, where aa erudition the most vast, the most 

* His Historical Account of two notable Corruptions of tiu Scrip- 
tures. 50 pp quarto. 



SIR ISAAC NEWTON. 






varied, and the most ready always supports an argu- 
ment well arranged and powerfully combined. * 
At this epoch of the life of Newton the reading ol 
religious books had become one of his most habitual 
occupations, and after he had performed the duties 
of his office, they formed, along with the conversa- 
tion of his friends, his principal amusement. He 
had then almost ceased to care for the sciences, and, 
IN we have already remarked, since the fatal epoch 
of 1693, he gave to the world only three really new 
scientific productions." 

Notwithstanding the prodigy which it involves, M. 
Biot has adopted 1712-1719 as the date of this criti- 
cal dissertation ; it is regarded as the composition 
of a man of seventy-two or seventy-five ; the read- 
ing of religious works is stated to have become one of 
his most habitual occupations, and such reading is 
said to have been one of his principal amusements ; 
and all this is associated with " the fatal epoch of 
1693," as if his illness at that time had been the 
cause of his abandoning science and betaking him- 
self to theology. Carrying on the same views, M. 
Biot asks, in reference to Sir Isaac's work on Pro- 
phecy, " How a mind of the character and force of 
Newton's, so habituated to the severity of mathe 
matical considerations, so exercised in the observa- 
tion of real phenomena, and so well aware of the 
conditions by which truth is to be discovered, could 
put together such a number of conjectures without 
noticing the extreme improbability of his interpreta- 
tions from the infinite number of arbitrary postulates 
on which he has founded them ?" We would apply 
the same question to the reasoning by which M. Biot 
fixes the date of the critical dissertation ; and we 
would ask how so eminent a philosopher could haz- 
ard such frivolous conjectures upon a subject on 
which he had not a single fact to guide his inquiries. 
The obvious tendency, though not the design, of the 
conclusion at which he arrives is injurious to the 



LETTERS TO LOCKE. 245 

memory of Newton, as well as to the interests of 
religion; and these considerations might have 
checked the temerity of speculation, even if it had 
been founded on better data. The Newtonian inter- 
pretation of the Prophecies, and especially that part 
which M. Biot characterizes as unhappily stamped 
with the spirit of prejudice, has been adopted by men 
of the soundest and most unprejudiced minds; and 
in addition to the moral and historical evidence by 
which it is supported, it may yet be exhibited in all 
the fulness of demonstration. But the speculation 
of Biot respecting the date of Newton's theological 
works was never maintained by any other person 
than himself, and is capable of being disproved by 
the most incontrovertible evidence. 

We have already seen, in the extract from Mr. 
Pryme's manuscript, that previous to 1692, when a 
shade is supposed to have passed over his gifted 
mind, Newton was well known by the appellation 
of an " excellent divine," a character which could 
not have been acquired without the devotion of many 
years to theological researches ; but, important as 
this argument would have been, we are fortunately 
not left to so general a defence. The correspond- 
ence of Newton with Locke, recently published by 
Lord King, places it beyond a doubt that he had be- 
gun his researches respecting the Prophecies before 
the year 1691, before the forty-ninth year of his 
age, and before the "fatal epoch of 1693." The 
following letter shows that he had previously dis- 
cussed this subject with his friend : 

SIR, Cambridge, Feb. 7, 1690-1. 

"I am sorry your journey proved to so little pur- 
pose, though it delivered you from the trouble of the 
company the day after. You have obliged me by 
mentioning me to my friends at London, and I must 
thank both you and my Lady Masham for your 
civilities at Gates, and for not thinking that I made 

A * 



246 IR ISAAC NEWTON. 

a long stay there. J hope we shall meet again in 
due time, and then I should be glad to have your 
judgment upon some of my mystical fancies. The 
Son of Man, Dan. vii. I take to be the same with the 
Word of God upon the White Horse in Heaven, 
Apoc. xii., for both are to rule the nations with a rod 
of iron ; but whence are you certain that the Ancient 
of Days is Christ ? Does Christ anywhere sit upon 
the throne 1 If Sir Francis Masham be at Gates, 
present, I pray, my service to him, with his lady, 
Mrs. Cudworth, and Mrs. Masham. Dr. Covel is 
not in Cambridge. I am your affectionate and " 
humble servant, " Is. NEWTON 

'Know you the meaning of Dan. x. 21. There 
is none that holdeth with me in these things but 
Mich, the prince." 

Having thus determined the date of those investi- 
gations which constitute his observations on the pro- 
phecies of holy writ, particularly the prophecies of 
Daniel and the Apocalypse, we shall proceed to fix 
the latest date of his historical account of two notable 
corruptions of the Scripture, in a letter to a friend. 

This work seems to have been a very early pro- 
duction of our author. It was written in the form 
of a letter to Mr. Locke, and at that time Sir Isaac 
seems to have been anxious for its publication. 
Afraid, however, of being again led into a contro- 
versy, and dreading the intolerance to which he 
might be exposed, he requested Mr. Locke, who 
was at that time meditating a voyage to Holland, 
to get it translated into French, and published on 
the Continent. Having abandoned his design of 
visiting Holland, Locke transmitted the manuscript, 
without Newton's name, to his learned friend M. Le 
Clerc, in Holland ; and it appears, from a letter of 
Le Clerc's to Locke, that he must have received it 
before the llth April, 1691. M. Le Clerc delayed 



LETTERS TO LOCKE. 247 

for a long time to take any steps regarding its pub- 
lication ; but in a letter dated January 20th, 1692, he 
announced to Locjte his intention of publishing the 
tract in Latin. When this plan was communicated 
to Sir Isaac, he became alarmed at the risk of de- 
tection, and resolved to stop the publication of his 
manuscript. This resolution was intimated to Mr. 
Locke in the following letter : 

" SIR, Cambridge, Feb. Uth, 1691-2. 

" Your former letters came not to my hand, but 
this I have. I was of opinion my papers had lain 
still, and am sorry to hear there is news about them. 
Let me entreat you to stop their translation and im- 
pression so soon as you can ; for I design to suppress 
them. If your friend hath been at any pains and 
charge, I will repay it, and gratify him. I am very 
glad my Lord Monmouth is till my friend, but intend 
not to give his lordship and you any farther trouble. 
My inclinations are to sit still. I am to beg his 
lordship's pardon for pressing into his company the 
last time I saw him. I had not done it, but that Mr. 
Paulin pressed me into the room. Miracles, of 
good credit, continued in the church for about two 
or three hundred years. Gregorius Thaumaturgus 
had his name from thence, and was one of the latest 
who was eminent for that gift ; but of their number 
and frequency I am not able to give you a just ac- 
count. The history of those ages is very imperfect. 
Mr. Paulin told me you had writ for some of Mr 
Boyle's red earth, and by that I knew you had the 
receipt. Your most affectionate and humble servant, 

" Is. NEWTON." 

Hence we see that this celebrated treatise, which 
Biot alleges to have been written between 1712 and 
1719, was actually in the hands of Le Clerc in Hol- 
land previous to the llth April, 1691, and conse- 
quently previous to the time of the supposed insanity 



248 SIR ISAAC NEWTON. 

of its author. Mr. Locke lost no time in obeying the 
request of his friend. Le Clerc instantly stopped the 
publication of the letter, and, as he had never learned 
the name of the author, he deposited the manuscript, 
which was in the handwriting of Mr. Locke, in the 
library of the Remonstrants, where it was afterward 
found, and was published at London in 1754, under 
the title of Two letters from Sir Isaac Newton to M. 
Le Clerc, a form which had never been given to it 
by its author. The copy thus published was a very 
imperfect one, wanting both the beginning* and the 
end, and erroneous in many places ; but Dr. Horsley 
has published a genuine edition, which has the form 
of a single letter to a friend, and was copied from a 
manuscript in Sir Isaac Newton's handwriting, in the 
possession of the Rev. Dr. Ekins, Dean of Carlisle. 

Having thus determined as accurately as possible 
the dates of the principal theological writings of Sir 
Isaac, we shall now proceed to give some account 
of their contents. 

The Observations on the Prophecies of Daniel and 
the Apocalypse of St. John were published in London 
in 1733, in one volume 4to. The work is divided 
into two parts, the first of which treats of the Pro- 
phecies of Daniel, and the second of the Apocalypse 
of St. John. It begins with an account of the dif- 
ferent books which compose the Old Testament ; and 
as the author considers Daniel to be the most dis- 
tinct in the order of time, and the easiest to be un- 
derstood, he makes him the key to all the prophetic 
books in those matters which relate to the "last time." 
He next considers the figurative language of the 
prophets, which he regards as taken " from the 
analogy between the world natural and an empire 
or kingdom considered as a world politic ;" the hea- 
vens and the things therein representing thrones and 
dynasties; the earth, with the things therein, the 

* The editor supplied the beginning down to the 13th page, where he 
mentions in a note that "thus far is not Sir Isaac's." 




OBSERVATIONS ON PROPHECY. 249 

"erior people ; and the lowest parts of the earth 
the most miserable of the people. The sun is put 
for the whole race of kings, the moon for the body 
of the common people, and the stars for subordinate 
: princes and rulers. In the earth, the dry land and 
the waters are put for the people of several nations. 
j Animals and vegetables are also put for the people 
i of several regions. When a beast or man is put for 
f a kingdom, his parts and qualities are put for the 
analogous parts and qualities of the kingdom ; and 
i when a man is taken in a mystical sense, his quali- 
i ties are often signified by his actions, and by the 
circumstances and things about him. In applying 
? these principles he begins with the vision of the 
'image composed of four different metals. This 
i image he considers as representing a body of four 
great nations which should reign in succession over 
the earth, viz. the people of Babylonia, the Persians, 
the Greeks, and the Romans ; while the stone cut out 
without hands is a new kingdom which should arise 
I after the four, conquer all those nations, become very 
great, and endure to the end of time. 

The vision of the four beasts is the prophecy of the 
four empires repeated, with several new additions. 
1 The lion with eagles' wings was the kingdom of 
Babylon and Media, which overthrew the Assyrian 
power. The beast like a bear was the Persian em- 
pire, and its three ribs were the kingdoms of Sardis, 
| Babylon, and Egypt. The third beast, like a leopard, 
I was the Greek empire, and its four heads and four 
1 wings were the kingdoms of Cassander, Lysimachus, 
Ptolemy, and Seleucus. The fourth beast, with its 
great iron teeth, was the Roman empire, and its ten 
horns were the ten kingdoms into which it was 
broken in the reign of Theodosius the Great. 

In the fifth chapter Sir Isaac treats of the king- 
doms represented by the feet of the image composed 
of iron and clay which did not stick to one another, 
and which were of different strength. These were 



250 SIR ISAAC NEWTON. 

the Gothic tribes called Ostrogoths, Visigoths, Van- 
dais, Gepidae, Lombards, Burgundians, Alans, &c. ; 
all of whom had the same manners and customs, 
and spoke the same language, and who, about the 
year 416 A. C. were all quietly settled in several 
kingdoms within the empire, not only by conquest, 
but by grants of emperor. 

In the sixth chapter he treats of the ten kingdoms 
represented by the ten horns'of the fourth beast, into 
which the western empire became divided about the 
time when Rome was besieged and taken by the 
Goths. These kingdoms were, 

1. The kingdom of the Vandals and Alans in Spain 
and Africa. 

2. The kingdom of Suevians in Spain. 

3. The kingdom of the Visigoths. 

4. The kingdom of the Alans in Gaul. 

5. The kingdom of the Burgundians. 

6. The kingdom of the Franks. 

7. The kingdom of the Britains. 

8. The kingdom of the Huns. 

9. The kingdom of the Lombards. 
10. The kingdom of Ravenna. 

Some of these kingdoms at length fell, and new 
ones sprung up ; but whatever was their subsequent 
number, they still retain the name of the ten kings 
from their first number. 

The eleventh horn of Daniel's fourth beast is shown 
in chapter vii. to be the Church of Rome in its triple 
character of a seer, a prophet, and a king ; and its 
power to change times and laws is copiously illus- 
trated in chapter viii. 

In the ninth chapter our author treats of the king- 
dom represented in Daniel by the ram and he-goat, 
:he ram indicating the kingdom of the Medes and 
Persians from the beginning of the four empires, and 
the he-goat the kingdom of the Greeks to the end 
of them. 

The prophecy of the seventy weeks, which had 






OBSERVATIONS ON PROPHECY. 251 



i hitherto been restricted to the first coming of our 
ISaviour, is shown to be a prediction of all the main 
Jperiods relating to the coming of the Messiah, the 
[times of his birth and death, the time of his rejection 
[by the Jews, the duration of the Jewish war by which 
[he caused the city and sanctuary to be destroyed, 
land the time of his second coming. 

In the eleventh chapter Sir Isaac treats "rith great 
[sagacity and acuteness of the time of our Saviour's 
[birth and passion, a subject which had perplexed 
[all preceding commentators. 

After explaining in the twelfth chapter the last 
prophecy of Daniel, namely, that of the scripture of 
truth, which he considers as a commentary on the 
vision of the ram and he-goat, he proceeds in the 
thirteenth chapter to the prophecy of the king who 
did according to his will, and magnified himself above 
every god, and honoured Mahuzzims, and regarded 
not the desire of women. He shows that the Greek 
empire, after the division of the Roman empire into 
the Greek and Latin empires, became the king who 
in matters of religion did according to his will, and 
in legislation exalted and magnified himself above 
every god. 

In the second part of his work on the Apocalypse 
of St. John, Sir Isaac treats, 1st, Of the time when 
the prophecy was written, which he conceives to 
have been during John's exile in Patmos, and before 
the epistle to the Hebrews and the epistles of Peter 
were written, which in his opinion have a reference 
to* the Apocalypse ; 2dly, Of the scene of the vision, 
and the relation which the Apocalypse has to the 
book of the law of Moses, and to the worship of God 
in the temple ; and, Sdly, Of the relation which the 
Apocalypse has to the prophecies of Daniel, and of 
the subject of the prophecy itself. 

Sir Isaac regards the prophecies of the Old and 
New Testaments, not as given to gratify men's curi 
osities, by enabling them to foreknow things, but that 



252 SIR ISAAC NEWTON. 

after they were fulfilled, they might be interpreted 
by the event, and afford convincing arguments that 
the woild is governed by Providence. He considers 
that there is so much of this prophecy already ful- 
filled as to afford to the diligent student sufficient 
instances of God's providence; and he adds, that 
" among the interpreters of the last age, there is 
scarce one of note who hath not made some discovery 
worth knowing, and thence it seems one may gather 
that God is about opening these mysteries. The 
success of others," he continues, " put me upon con- 
sidering it, and if I have done any thing which may 
be useful to following writers, I have my design." 
, Such is a brief abstract of this ingenious work, 
which is characterized by great learning, and marked 
with the sagacity of its distinguished author. The 
same qualities of his mind are equally conspicuous 
in his Historical Account of Two Notable Corruptions 
of Scripture. 

This celebrated treatise relates to two texts in the 
Epistles of St. John and St. Paul. The first of these 
is in 1 John v. 7. " For there are three that bear 
record in heaven, the Father, the Son, and the Holy 
Ghost, and these three are one." This text he con- 
siders as a gross corruption of Scripture, which had. 
its origin among the Latins, who interpreted the 
Spirit, Water, and Blood to be the Father, Son, and 
Holy Ghost, in order to prove them one. With the 
same view Jerome inserted the Trinity in express 
words in his version. The Latins marked his varia- 
tions in the margins of their books; and in the 
twelfth and following centuries, when the disputa- 
tions of the schoolmen were at their height, the 
variation began to creep into the text in transcribing. 
After the invention of printing, it crept out of the 
Latin into the printed Greek, contrary to the author- 
ity of all the Greek manuscripts and ancient ver- 
sions; and from the Venetian press it went soon 
after into Greece. After proving these positions 



CORRUPTIONS OF SCRIPTURE. 253 

Sir Isaac gives the following paraphrase of this re- 
'* markable passage, which is given in italics. 

" Who is he that overcometh the world, but he that 
$ lelieveth that Jesus is the Son of God, that Son spoken 
I of in the Psalms, where he saith, ' thou art my Son ; 
I this day have 1 begotten thee.' This is he that, after 
I the Jews had long expected him, came, first in a mor- 
I tal body, by baptism of water, and then in an immor- 
I tal one, by shedding his blood upon the cross and 
I rising again from the dead ; not by water only, but 
\ by water and blood ; being the Son of God, as well 
by his resurrection from the dead (Acts xiii. 33), as 
I by his supernatural birth of the virgin (Luke i. 35). 
j And it is the Spirit also that, together with the water 
and blood, beareth witness of the truth of his coming ; 
because the Spirit is truth ; and so a fit and unexcep- 
tionable witness. For there are three that bear record 
of his coming ; the Spirit, which he promised to send, 
and which was since shed forth upon us in the form 
of cloven tongues, and in various gifts ; the baptism 
of water, wherein God testified ' this is my beloved 
Son ;' and the shedding of his blood, accompanied with 
his resurrection, whereby he became the most faith- 
ful martyr, or witness, of this truth. And these three, 
the spirit, the baptism, and passion of Christ, agree 
in witnessing one and-the same thing (namely, that 
the Son of God is come) ; and, therefore, their evi- 
dence is strong : for the law requires but two con- 
I senting witnesses, and here we have three : and if 
! we receive the witness of men, the threefold witness of 
God, which he bare of his Son, by declaring at his 
baptism 'this is my beloved Son,' by raising him 
from the dead, and by pouring out his Spirit on us 
is greater; and, therefore, ought to be more readily 
received." 

While the Latin Church was corrupting the pre- 
ceding text, the Greek Church was doing the same 
to St. Paul's 1st Epistle to Timothy iii. 16. Great 
is the mystery of godliness, God manifest in the flesh. 



254 SIR ISAAC NEWTON. 

According to Sir Isaac, this reading was effected by 
changing b into ec, the abbreviation of e**, and after 
proving this by a learned and ingenious examination 
of ancient manuscripts, he concludes that the read- 
ing should be Great is the mystery of Godliness who 
(viz. our Saviour) was manifest in the flesh. \ 

As this learned dissertation had the effect of de- 
priving the defenders of the doctrine of the Trinity 
of the aid of two leading texts, Sir Isaac Newton has 
been regarded as an Antitririitarian ; but such a con- 
clusion is not warranted by any thing which he has 
published ;* and he distinctly warns us, that his ob- 
ject was solely to " purge the truth of things spu- 
rious." We are disposed, on the contrary, to think 
that he declares his belief in the doctrine of the 
Trinity when he says, " In the eastern nations, and 
for a long time in the western, the faith subsisted 
without this text ; and it is rather a danger to reli- 
gion than an advantage, to make it now lean upon a 
bruised reed. There cannot be better service done 
to the truth than to purge it of things spurious ; and 
therefore, knowing your prudence and calmness of 
temper, I am confident I shall not offend you by tell- 
ing you my mind plainly ; especially since it is no 
article of faith, no point of discipline, nothing but a 
criticism concerning a text of Scripture which I am 
going to write about." The word faith in the pre- 
ceding passage cannot mean faith in the Scriptures in 
general, but faith in the particular doctrine of the 
Trinity ; for it is this article of faith only to which 
the author refers when he deprecates its leaning on 
a bruised reed. But, whatever be the meaning of 
this passage, we know that Sir Isaac was greatly 

* M. Biot has well remarked that there is absolutely nothing in the 
writings of Newton to justify, or even to authorize, the idea that he was 
an Antitrinitarian. This passage is strangely omitted in the English 
translation of Blot's Life of Newton. We do not know upon what au- 
thority Dr. Thomson states, in his History of the Royal Society, that 
Newton " did not believe in the Trinity," and that Dr. Horsley considered 
Newton's papers unfit for publication, because they contained proofs of 
his hostility to that doctrine. 



LEXICON PROPHETICITM. 255 

offended at Mr. Whiston for having represented him 
as an Arian ; and so much did he resent the conduct 
of his friend in ascribing to him heretical opinions, 
that he would not permit him to be elected a Fellow 
of the Royal Society while he was President.* 

The only other religious works which were com- 
posed by Sir Isaac Newton were his Lexicon Pro- 
pheticum, to which was added a Dissertation on the 
sacred cubit of the Jews, and Four Letters addressed 
to Dr. Bentley i containing some arguments in proof of 
a Deity. 

The Lexicon Propheticum was left incomplete, and 
has not been published ; but the Latin Dissertation 
which was appended to it, in which he shows that 
the cubit was about 26 Roman unciae, was published 
in 1737 among the Miscellaneous Works of Mr. John 
Greaves. 

Upon the death of the Honourable Robert Boyle, 
on* the 30th of December, 1691, it was found, by a 
codicil to his will, that he had left a revenue of 507. 
per annum to establish a lectureship, in which eight 
discourses were to be preached annually in one of 
the churches of the metropolis, in illustration of the 
evidences of Christianity, and in opposition to the 
principles of infidelity. Dr. Bentley, though a very 
young man, was appointed to preach the first course 
of sermons, and the manner in which he discharged 
this important duty gave the highest satisfaction, not 
only to the trustees of the lectureship, but to the 
public in general. In the first six lectures Bentley 
exposed the folly of atheism even in reference to the 
present life, and derived powerful arguments for the 
existence of a Deity from the faculties of the soul, 
and the structure and functions of the human frame 
In order to complete his plan, he proposed to devote 
his seventh and eighth lectures to the demonstration 
of a Divine Providence from the physical constitu- 

* Whiston's Memoirs of his own Life, p. 178, 249, 250 Edit #8 J 



256 SIR ISAAC NEWTON. 

tion of the universe, as established in the Principia. 
In order to qualify himself for this task, he received 
from Sir Isaac written directions respecting a list of 
books necessary to be perused previous to the study 
of that work ;* and having made himself master of 
the system which it contained, he applied it with 
irresistible force of argument to establish the ex- 
istence of an overruling mind. Previous to the pub- 
lication of these lectures, Bentley encountered a 
difficulty which he was not able to solve, and he 
prudently transmitted to Sir Isaac during 1692 a 
series of queries on the subject. This difficulty oc- 
curred in an argument urged by Lucretius, to prove 
the eternity of the world from an hypothesis of de- 
riving the frame of it by mechanical principles from 
matter endowed with an innate power of gravity, and 
evenly scattered throughout the heavens. Sir Isaac 
'willingly entered upon the consideration of the sub- 
>>*ct, and transmitted his sentiments to Dr. Bentley 
in the four letters which have been noticed in a pre- 
ceding chapter. 

In the firstf of these letters Sir Isaac mentions 
that when he wrote his treatise about our system, 
viz. the Third Book of the Principia, " he had an 
eye upon such principles as might work, with con- 
sidering men, for the belief of a Deity, and he ex- 
presses his happiness that it has been found useful 
for that purpose. In answering the first query of 
Dr. Bentley, the exact import of which we do not 
know, he states, that, if matter were evenly diffused 
through a finite space, and endowed with innate 
gravity, it would fall down into the middle of the 
space, and form one great spherical mass ; but if it 
were diffused through an infinite space, some of it 
would collect into one mass, and some into another, 

* Dr. Monk's Life of Bentley, p. 31. 

t Dated December 10th, 1692. This letter is endorsed, in Bentley's 
hand, "Mr. Newton's answer to some queries sent by me after I had 
preached my two last sermons." Monk's Life of Bentley, p. 34. note. 



LETTERS TO DR. BENTLEY. 257 

so as to form an infinite number of great masses. 
In this manner the sun and stars might be formed if 
the matter were of a lucid nature. But he thinks it 
inexplicable by natural causes, and to be ascribed to 
the counsel and contrivance of a voluntary Agent, 
that the matter should divide itself into two sorts, 
part of it composing a shining body like the sun, and 
part an opaque body like the planets. Had a natural 
and blind cause, without contrivance and design, 
placed the earth in the centre of the moon's orbit, 
and Jupiter in the centre of his system of satellites, 
and the sun in the centre of the planetary system, 
the sun would have been a body like Jupiter and the 
earth, that is, without light and heat, and conse- 
quently he knows no reason why there is only one 
body qualified to give light CLid heat to all the rest, 
but because the Author of the system thought it con- 
venient, and because one was sufficient to warm 
and enlighten all the rest. 

To the second query of Dr. Bentley, he replies 
that the motions which the planets now have could 
not spring from any natural cause alone, but were 
impressed by an intelligent Agent. " To make such 
a system with all its motions required a cause which 
understood and compared together the quantities of 
matter in the several bodies of the sun and planets, 
and the gravitating powers resulting from thence ; 
the several distances of the primary planets from 
the sun, and of the secondary ones from Saturn Ju- 
piter, and the earth, and the velocities with which 
those planets could revolve about those quantities 
of matter in the central bodies ; and to compare and 
adjust all these things together in so great a variety 
of bodies, argues that cause to be not blind and for- 
tuitous, but very well skilled in mechanics and geo- 
metry." 

In "the second* letter, he admits that the spherical 

* Dated Jan. 17th, 1692-3 

Y2 



258 SIR ISAAC NEWTON. 

mass formed by the aggregation of particles would 
affect the figure of the space in which the matter 
was diffused, provided the matter descends directly 
downwards to that body, and the body has no diurnal 
rotation ; but he states, that by earthquakes loosen- 
ing the parts of this solid, the protuberance might 
sink a little by their weight, and the mass by degrees 
approach a spherical figure. He then proceeds to 
correct an error of Dr. Bentley's in supposing that 
all infinites are equal. He admits that gravity might 
put the planets in motion, but he maintains that, 
without the Divine power, it could never give them 
such a circulating motion as they have about the 
sun, because a proper quantity of a transverse mo- 
tion is necessary for this purpose ; and he concludes 
that he is compelled to ascribe the frame of this 
system to an intelligent Agent. 

The third letter contains opinions confirming or 
correcting several positions which Dr. Bentley had 
laid down, and he concludes it with a curious exam- 
ination of the opinion of Plato, that the motion of 
the planets is such as if they had been ail created 
by God in some region very remote from our sys- 
tem, and let fall from thence towards the sun, their 
falling motion being turned aside into a transverse 
one whenever they arrived at their several orbits. 
Sir Isaac shows that there is no common place such 
as thai conjectured by Plato, provided the gravi- 
tating power of the sun remains constant ; but that 
Plato's affirmation is true if we suppose the gravi 
tatmg power of the sun to be doubled at that mo- 
ment of time when they all arrive at their several 
orbits. " If we suppose," says he, " the gravity of 
all the planets towards the sun to be of such a quan- 
tity as it really is, and that the motions of the 
planets are turned upwards, every planet will ascend 
to twice its height from the sun. Saturn will as- 
cend till he be twice as high from the sun as he is 
at present, and no higher; Jupiter will ascend as 



LETTERS TO DR. BENTLEY. 259 

high again as at present, that is, a little above the 
orb of Saturn; Mercury will ascend to twice his 
present height, that is, to the orb of Venus ; and so 
of the rest ; and then, by falling down again from 
the places to which they ascended, they will arise 
i again at their several orbs with the same velocities 
they had at first, and with which they now revolve. 
" But if so soon as their motions by which they 
revolve are turned upwards, the gravitating power 
! of the sun, by which their ascent is perpetually re- 
tarded, be diminished by one-half, they will now 
ascend perpetually, and all of them, at all equal dis- 
tances from the sun, will be equally swift. Mer- 
cury, when he arrives at the orb of Venus, will be 
as swift as Venus ; and he and Venus, when they 
arrive at the orb of the earth, will be as swift as the 
earth ; and so of the rest. If they begin all of them 
to ascend at once, and ascend in the same line, they 
i will constantly, in ascending, become nearer and 
I nearer together, and their motions will constantly 
[approach to an equality, and become at length 
slower than any motion assignable. Suppose, there- 
fore, that they ascended till they were almost con- 
tiguous, and their motions inconsiderably little, and 
(that all their motions were at the same moment of 
time turned back again, or, which comes almost to 
ithe same thing, that they were only deprived of their 
I motions, and let fall at that time, they would all at 
once arrive at their several orbs, each with the ve- 
rt locity it had at first ; and if their motions were then 
I turned sideways, and at the same time the gravi- 
tating power of the sun doubled, that it might be 
strong enough to retain them in their orbs, they 
would revolve in them as before their ascent. But 
if the gravitating power of the sun was not doubled, 
they would go away from their orbs into the highest 
heavens in parabolical lines."* 

* " These things," says he, " follow from my Princip. Matk. lib. i. 
prop. 33, 34, 35, 36 " 



260 SIR ISAAC NEWTON. 

In the fourth letter* he states, that the hypothesi 
that matter is at first evenly diffused through th 
universe is in his opinion inconsistent with th 
hypothesis of innate gravity without a supernature 
power to reconcile them, and therefore it infers 
Deity. " For if there be innate gravity, it is impos 
sible now for the matter of the earth and all th 
planets and stars to fly up from them, and becom 
evenly spread throughout all the heavens without 
supernatural power; and certainly that which ca: 
never be hereafter without a supernatural powei 
could never be heretofore without the same power. 

These letters, of which we have endeavoured t 
give a brief summary, will well repay the mos 
attentive perusal by the philosopher as well as th 
divine. They are written with much perspicuity o 
language and great power of thought, and the; 
contain results which incontestably prove that thei 
author was fully master of his noblest faculties 
and comprehended the profoundest parts of his ow: 
writings.! 

The logical acuteness, the varied erudition, an 
the absolute freedom from all prejudice which shin 
throughout the theological writings of Newtor 
might have protected them from the charge of ha\ 
ing been written in his old age, and at a time whe 
a failure -of mind was supposed to have unfitted hir 
for his mathematical investigations. But it is fortu 
nate for his reputation, as well as for the interest 
of Christianity, that we have been able to prove th 
incorrectness of such insinuations, and to exhibi 
the most irrefragable evidence that all the theologicc 

* Dated February llth, 1693. 

t The originals of these four letters to Bentley " were given by D 
Richard Bentley to Cumberland, his nephew, and executor, while a sti 
dent at Trinity College, and were printed by him in a separate pamphh 
in 1756. This publication was reviewed by Dr. Samuel Johnson in th 
Literary Magazine, vol. i. p. 89. See Johnson's Works, vol. ii. p. 32i 
The original letters are preserved in Trinity College, to which societ 
they were given by Cumberland a short time before his death." Monk' 
Life of Bentley, p. 33, note. 



THEOLOGICAL STUDIES. 261 

writings of Newton were composed in the vigour 
)f his life, and before the crisis of that bodily dis- 
>rder which is supposed to have affected his reason. 
The able letters to Dr. Bentley were even written 
n the middle of that period when want of sleep and 
ippetite had disturbed the serenity of his mind, and 
mable us to prove that this disturbance, whatever 
vas its amount, never affected the higher functions 
)f his understanding. 

When a philosopher of distinguished eminence, 
ind we believe not inimical to the Christian faith, 
as found it necessary to make a laboured apology 
or a man like Newton writing on theological sub- 
ects, and has been led to render that apology more 
omplete by referring this class of his labours to a 
nind debilitated by age and weakened by its pre- 
ious aberrations, it may be expected from an Eng- 
sh biographer, and one who acknowledges the 
mportance of revealed truth, and the paramount 
nterest of such subjects above all secular studies, 
o suggest the true origin of Newton's theological 
iquiries. 

When a mind of great and acknowledged power 
rst directs its energies to the study of the material 
niverse, no indications of order attract his notice, 
rid no proofs of design call forth his admiration, 
n the starry firmament he sees no bodies of stupen- 
ous magnitude, and no distances of immeasurable 
jan. The two great luminaries appear vastly in- 
'edor in magnitude to many objects around him, and 
le greatest distances in the heavens seem even in- 
erior to those which his own eye can embrace on 
he surface of the earth. The planets, when ob- 
erved with care, are seen to have a motion among 
he fixed stars, and to vary in their magnitude and 
istances, but these changes appear to follow no 
aw. Sometimes they move to the east, sometimes 
o the west, sometimes towards the north, and 
ometimes towards the south, and at other times 



262 SIR ISAAC NEWTON. 



, 



they are absolutely stationary. No system, in short, 
appears, and no general law seems to direct their 
motions. By the observations and inquiries of 
astronomers, however, during successive ages, a 
regular system has been 'recognised in this chaos of 
moving bodies, and the magnitudes, distances, and 
revolutions of every planet which composes it has 
been determined with the most extraordinary accu- 
racy. Minds fitted and prepared for this species of 
inquiry are capable of understanding the great 
variety of evidence by which the truth of the plan- * 
etary system is established ; but thousands of indi- 
viduals who are even distinguished in other branches 
of knowledge are incapable of such researches, and 
view with a skeptical eye the great and irrefragable 
truths of astronomy. 

That the sun is stationary in the centre of our 
system, that the earth moves round the sun, and 
round its own axis, that the earth is 8000 miles in 
diameter, and the sun one hundred and ten times as 
large, that the earth's orbit is 190 millions of miles 
in breadth, and that if this immense space were 
filled with light, it would appear only like a luminous 
point at the nearest fixed star, are positions abso- 
lutely unintelligible and incredible to all who have 
not carefully studied the subject. To millions of 
our species, then, the great book of nature is ab- 
solutely sealed, though it is in the power of all to 
unfold its pages, and to peruse those glowing pas- 
sages which proclaim the power and wisdom of its 
mighty Author. 

The book of revelation exhibits to us the same 
peculiarities as that of nature. To the ordinary 
eye it presents no immediate indications of its 
Divine origin. Events apparently insignificant- 
supernatural interferences seemingly unnecessary 
doctrines almost contradictory and prophecies 
nearly unintelligible occupy its pages. The history 
of the fall of man of the introduction of moral 



THEOLOGICAL STUDIES. 263 

and physical evil the prediction of a Messiah the 
actual advent of our Saviour his instructions his 
miracles his death his resurrection and the sub- 
sequent propagation of his religion by the unlettered 
;ishermen of Galilee, are each a stumblingblock to 
;:he wisdom of this world. The youthful and vigor- 
ous mind, when first summoned to peruse the Scrip- 
;ures, turns from them with disappointment. It 
recognises in them no profound science no secular 
pisdom no Divine eloquence no disclosures of 
jiature's secrets no direct impress of an Almighty 
pand. But, though the system of revealed truth 
[which this book contains is, like that of the universe, 
Concealed from common observation, yet the labours 
JDf centuries have established its Divine origin, and 
developed in all its order and beauty the great plan 
pf human restoration. In the chaos of its incidents 
we discover the whole history of our species, 
whether it is delineated in events that are past or 
shadowed forth in those which are to come, from 
;he creation of man and the origin of evil, to the 
extinction of his earthly dynasty and the commence- 
ment of his immortal career. 
The antiquity and authenticity of the books which 

ompose the sacred canon, the fulfilment of its 
prophecies, the miraculous works of its founder, 
his death and resurrection, have been demonstrated 
jto all who are capable of appreciating the force of 
historical evidence; and in the poetical and prose 
|bompositions of the inspired authors we discover a 
system of doctrine and a code of morality traced in 
characters as distinct and legible as the most unerr- 
ing truths in the material world. False systems of 
religion have indeed been deduced from the sacred 
record, as false systems of the universe have 
sprung from the study of the book of nature, but 
the very prevalence of a false system proves the 
existence of one that is true ; and though the two 

classes of facts necessarily depend on different 



264 SIR ISAAC NEWTON. 

kinds of evidence, yet we scruple not to say that 
the Copernican system is not more demonstrably 
true than the system of theological truth contained 
in the Bible. If men of high powers, then, are still 
found, who are insensible to the evidence which 
sustains the system of the universe, need we won- 
der that there are others whose minds are shut 
against the effulgent evidence which intrenches the 
strongholds of our faith. 

If such, then, is the character of the Christian 
faith, we need not be surprised that it was embraced 
and expounded by such a genius as Sir Isaac New- 
ton. Cherishing its doctrines, and leaning on its 
promises, he felt it his duty, as it was his pleasure, 
to apply to it that intellectual strength which had 
successfully surmounted the difficulties of the ma- 
terial universe. The fame which that success pro- 
cured him he could not but feel to be the breath of 
popular applause, which administered only to his 
personal feelings ; but the investigation of the sacred 
mysteries, while it prepared his own mind for its 
final destiny, was calculated to promote the spiritual 
interests of thousands. This noble impulse he did 
not hesitate to obey, and by thus uniting philosophy 
with religion, he dissolved the league which genius 
had formed with skepticism, and added to the cloud 
of witnesses the brightest name of ancient or of 
modern times. 



HIS SCALE OF HEAT. 265 



CHAPTER XVII. 

Tfte minor Discoveries and Inventions of Neivton His Researches on 
Heat On Fire and Flame On Elective Attraction On the Struc- 
ture of Bodies His supposed Attachment to AlchymyHis Hypothe- 
sis respecting Ether as the Cause of Light and Gravity On the Ex- 
citation of Electricity in ^lassHis Reflecting Sextant invented 
before 17Q& His Reflecting Microscope His Prismatic Reflector* as a 
Substitute for the small Speculum of Reflecting Telescopes Hit 
Method of varying the Magnifying Power of Newtonian Telescopes 
His Experiments on Impressions on the Retina. 

IN the preceding chapters we have given an ac- 
count of the principal labours of Sir Isaac Newton ; 
but there still remain to be noticed several of his 
minor discoveries and inventions, which could not 
properly be introduced under any general head. 

The most important of these, perhaps, are his 
chymical researches, which he seems to have pur- 
sued with more or less diligence from the time 
when he first witnessed the practical operations of 
chymistry during his residence at the apothecary's 
at Grantham. . His first chymical experiments were 
probably made on the alloys of metals, for the pur- 
pose of obtaining a good metallic composition for 
the specula of reflecting telescopes. In his paper 
on thin plates he treats of the combinations of solids 
and fluids ; but he enters more largely on these and 
other subjects in the queries published at the end 
of his Optics. 

One of his most important chymical papers is 
his Tabula quantltatum et graduum caloris, which 
was published in the Philosophical Transactions. 
This short paper contains a comparative scale of 
temperature from that of melting ice to that of a 
small kitchen coal-fire. The following are the 
principal points of the scale, the intermediate 
Z 



266 SIR ISAAC NEWTON. 

degrees of heat having been determined with great 
care. 

Degrees Equal Parts 

of Ht. of Heat. 

Freezing point of water. 

1 12 Blood-heat. 

2 24 Heat of melting wax. 

3 48 Melting point of equal parts of tin 

and bismuth. 

4 96 Melting point of lead. 

5 192 Heat of a small coal-fire. 

The first column of this table contains the degrees! 
of heat in arithmetical progression, and the second! 
in geometrical progression, the second degree being! 
twice as great as the first, and so on. It is obvious 
from this table, that the heat at which equal parts 
of tin and bismuth melt is four times greater than 
that of blood-heat, the heat of melting lead eight 
times greater, and the heat of a small coal-fire six- 
teen times greater. 

This table was constructed by the help of a ther-s 
mometer, and of red-hot iron. By the former he! 
measured all heats as far as that of melting tinji 
and by the latter he measured all the higher heats. 
For the heat which heated iron loses in a given time 
is as the total heat of the iron ; and therefore, if the 
times of cooling are taken equal, the heats will be 
in a geometrical progression, and may therefore be 
easily found by a table of logarithms. 

He found by a thermometer constructed with lin- 
seed oil, that if the oil, when the thermometer was 
placed in melting snow, occupied a space of 1000 
parts, the same oil, rarefied with one degree of heat, 
or that of the human body, occupied a space of 
10256 ; in the heat of water beginning to boil, a 
space of 10705 ; in the heat of water boiling vio- 
lently, 10725 ; in the heat of melted tin beginning tc 
cool, and putting on the consistency of an amalgam. 



HIS SCALE OF HEAT. 267 

11516, and when the tin had become solid, 11496. 
Hence the oil was rarefied in the ratio of 40 to 39 
by the heat of the human body ; of 15 to 14 by the 
heat of boiling water; of 15 to 13 in the heat of 
melting tin beginning to solidify ; and of 23 to 20 in 
the same tin when solid. The rarefaction of air 
was, with the same heat, ten times greater than that 
of oil, and the rarefaction of oil fifteen times greater 
than that of spirit of wine. By making the heats 
of oil proportional to its rarefaction, and by calling 
the heat of the human body 12 parts, we obtain the 
heat of water beginning to boil, 33 ; of water boil- 
ing violently, 34 ; of melted tin beginning to solidify, 
72 ; and of the same become solid, 70. 

Sir Isaac then heated a sufficiently thick piece 
bf iron till it was red-hot ; and having fixed it in a 
cold place, where the wind blew uniformly, he put 
upon it small pieces of different metals and other 
fusible bodies, and noted the times of cooling, till 
all the particles, having lost their fluidity, grew cold, 
and the heat of the iron was equal to that of the 
human body. Then, by assuming that the excesses 
of the heats of the iron and of the solidified par- 
ticles of metal above the heat of the atmosphere, 
were in geometrical progression when the times 
were in arithmetical progression, all the heats were 
obtained. The iron was placed in a current of air, 
in order that the air heated by the iron might always 
I be carried away by the wind, and that cold air 
i might replace it with a uniform motion; for thus 
equal parts of the air were heated in equal times, 
and received a heat proportional to that of the iron. 
But the heats thus found had the same ratio to one 
another with the heats found by the thermometer ; 
and hence he was right in assuming that the rare- 
factions of the oil were proportional to its heats. 

Another short chymical paper by Sir Isaac New- 
ton has been published by Dr. Horsley, It is enti- 



268 SIR ISAAC NEWTON. 

tied De Natura Acidorum, but is principally occupied 
with a number of brief opinions on chymical sub- 
jects. This paper was written later than 1687, as it 
bears a reference to the Principia ; and the most im- 
portant facts which it contains seem to have been 
more distinctly reproduced in the queries at the end 
of the Optics. 

The most important of these queries relate to fire, 
flame, and electric attractions, and as they were re- 
vised in the year 1716 and 1717, they may be regarded 
as containing the most matured opinions of their 
author. Fire he regards as a body heated so hot as 
to emit light copiously, and flane as a vapour, fume, 
or exhalation heated so hot as to shine. In his long 
query on elective attractions, he considers the small 
particles of bodies as acting upon one another at 
distances so minute as to escape observation. When 
salt of tartar deliquesces, he supposes that this arises 
from an attraction between the saline particles and 
the aqueous particles held in solution in the atmos- 
phere, and to the same attraction he ascribes it that 
the water will not distil from the salt of tartar with- 
out great heat. For the same reason sulphuric acid 
attracts water powerfully, and parts with it with 
great difficulty. When this attractive force becomes 
very powerful, as in the union between sulphuric 
acid and water, so as to make the particles " coalesce 
with violence," and rush towards one another with 
an accelerated motion, heat is produced by the mix- 
ture of the two fluids. In like manner, he explains 
the production of flame from the mixture of cold 
fluids, the action of fulminating powders, the com- 
bination of iron filings with sulphurand all the 
other chymical phenomena of precipitation, combi- 
nation, solution, and crystallization, and the mechan- 
ical phenomena of cohesion and capillary attrac- 
tion. He ascribes hot springs, volcanoes, fire-damps, 
mineral coruscations, earthquakes, hot suffocating 



ELECTIVE ATTRACTION. 269 

exhalations, hurricanes, lightning, thunder, fiery 
meteors, subterraneous explosions, land-slips, ebul- 
litions of the sea, and waterspouts, to sulphureous 
steams abounding in the bowels of the earth, and 
fermenting with minerals, or escaping into the atmos- 
phere, where they ferment with acid vapours fitted 
to promote fermentation. 

In explaining the structure of solid bodies, he is 
of opinion, "that the smallest particles of matter 
may cohere by the strongest attractions, and com- 
pose bigger particles of weaker virtue ; and many 
of these may cohere and compose bigger particles 
whose virtue is still weaker ; and so on for divers 
successions, until the progression end in the biggest 
particles, on which the operations in chymistry and 
the colours of natural bodies depend, and which, by 
adhering, compose bodies of a sensible magnitude. 
If the body is compact, and bends or yields inward 
to pression, without any sliding of its parts, it is hard 
and elastic, returning to its figure with a force rising 
from the mutual attraction of its parts. If the parts 
slide upon one another, the body is malleable or soft. 
If they slip easily, and are of a fit size to be agitated 
by heat, and the heat is big enough to keep them in 
agitation, the body is fluid ; and if it be apt to stick 
to things, it is humid ; and the drops of every fluid 
affect a round figure, by the mutual attraction of their 
parts, as the globe of the earth and sea affects a 
round figure, by the mutual attraction of its parts, by 
gravity." 

Sir Isaac then supposes, that, as the attractive 
force of bodies can reach but to a small distance from 
them, " a repulsive virtue ought to succeed ;" and he 
considers such a virtue as following from the reflec- 
tion of the rays of light, the rays being repelled with- 
Dut the immediate contact of the reflecting body, and 
also from the emission of light, the ray, as soon as 
it is shaken off from a shining body by the vibrating 
motion of the parts of the body, getting beyond the 
Z2 



270 SIR ISAAC NEWTON. 

reach of attraction, and being driven away with ex*' 
ceeding great velocity by the force of reflection.* 

Many of the chymical views which Sir Isaac thus 
published in the form of queries were in his own 
lifetime illustrated and confirmed by Dr. Stephen 
Hales, in his book on Vegetable Statics^a, work of 
great originality, which contains the germ of" some 
of the finest discoveries in modern chynustry. 

Although there is no reason to suppose that Sir 
Isaac Newton was a believer in the' doctrines of 
alchymy, yet we are informed by the Reverend Mr. 
Law that he had been a diligent student of Jacob 
Behmen's writings, and that there were found among 
his papers copious abstracts from them in his own 
handwriting.f He states also that Sir Isaac, together 
with one Dr. Newton, his relation, had, in the earlier 
part of his life, set up furnaces, and were for several 
months at work in quest of the philosopher's tinc- 
ture. These statements may receive some confir- 
mation from the fact, that there exist among the 
Portsmouth papers many sheets, in Sir Isaac's own 
writing, of Flammel's Explication of Hieroglyphic 
Figures, and in another hand, many sheets of Wil- 
liam Yworth's Processus Mysteni Magni Philosophi- 
cus, and also from the manner in which Sir Isaac 
requests Mr. Aston to inquire after one Borry in 
Holland, who always went clothed in green, and who 
was said to possess valuable secrets ; but Mr. Law 
has weakened the force of his own testimony, when 

* Mr. Herschel, in his Treatise on Light, $ 553, has maintained that 
Newton's Doctrine of Reflection is accordant with Ihe idea that the 
attractive force extends beyond the repulsive or reflecting force. In the 
query above referred to, Sir Isaac, in the most distinct mauner, places 
the sphere of the reflecting force without that of the attractive one. 

t In a tract annexed to his Appeal to all that doubt or disbelieve the 
truths of the Gospel. See Gent. Mag. 1782, vol. lii. p. 227, 239. 

It is stated in a letter of Mr. Law's, quoted in this magazine, that 
Charles I. was a diligent reader and admirer of Jacob Behmen ; that ho 
sent a well-qualified person from England to Goerlitz, in Upper Lusatia, 
to acquire the German language, and to collect every anecdote he could 
meet with there relative to this great alchymist. 



HYPOTHESIS OF ETHER. 271 

he asserts that Newton borrowed the doctrine of 
attraction from Behmen's first three propositions of 
eternal nature. 

On the 7th December, 1675, Sir Isaac Newton com- 
municated to the Royal Society a paper entitled 
An hypothesis explaining -properties of light, in which 
he, for the first time, introduces his opinions respect- 
ing ether, and employs them to explain the nature 
of light, and the cause of gravity. "He was in- 
duced,' 1 he says, "to do this, because he had observed 
the heads of some great virtuosos to run much upon 
hypotheses, and he therefore gave one which he was 
inclined to consider as the most probable, if he were 
obliged to adopt one."* 

This hypothesis seems to have been afterward a 
subject of discussion between him and Mr. Boyle, to 
whom he promised to communicate his opinion more 
fully in writing. He accordingly addressed to him a 
long letter, dated February 28th, 1678-9, in which 
he explains his views respecting ether, and employs 
them to account for the refraction of light, the co- 
hesion of two polished pieces of metal in an exhausted 
receiver, the adhesion of quicksilver to glass tubes, 
the cohesion of the parts of all bodies, the cause 
of filtration, the phenomena of capillary attraction, 
the action of menstrua on bodies, the transmu- 
tation of gross compact substances into aerial ones, 
and the cause of gravity. From the language used 
in this paper, we should be led to suppose that Sir 
Isaac had entirely forgotten that he had formerly 
treated the general subject of ether, and applied it 
to the explanation of gravity. " I shall set down," 
says he, " one conjecture more which came into my 
mind now as I was writing this letter ; it is about the 
cause of gravity" which he goes on to explain ;| and 

* Tn a letter to Dr. Halley, dated June 20th, 1686, Sir Isaac refers to 
this paper, and observes, that it is only to be looked upon as one of hia 
guesses that he did not rely upon. 

t See page 2731 



SIR ISAAC NEWTON. 

he concludes by saying, that " he has so little fancy 
to things of this nature, that, had not your encourage* 
ment moved me to it, I should never, I think, thus far 
have set pen to paper about them." 

These opinions, however, about the existence of 
ether, Newton seems to have subsequently re- 
nounced; for in the manuscript in the possession 
of Dr. J. C. Gregory, which we have already men- 
tioned, and which was written previous to 1702, he 
states, that ether is neither obvious to our senses, 
nor supported by any arguments, but is a gratuitous 
assumption, which, if we are to trust to reason and 
to our senses, must be banished from the nature of 
things ; and he goes on to establish, by various argu* 
ments, the validity of this opinion. This renuncia- 
tion of his former hypothesis probably arose from 
his having examined more carefully some of the 
phenomena which he endeavoured to explain by it. 
Those of capillary attraction, for example, he had 
ascribed to the ether " standing rarer in the very sen- 
sible cavities of the capillary tubes than without 
them," whereas he afterward discovered their true 
cause, and ascribed them to the reciprocal attraction 
of the tube and the fluid. But, however this may 
be, there can be no doubt that he resumed his early 
opinions before the publication of his Optics, which 
may be considered as containing his views upon this 
subject. 

The queries which contain these opinions are the 
18th-24th, all of which appeared for the first time in 
the second English edition of the Optics. If a body 
is either heated or loses its heat when placed in 
vacuo, he ascribes the conveyance of the heat in 
both cases " to the vibration of a much subtiler me- 
dium than air ;" and he considers this medium as the 
same with that by which light is refracted and re- 
flected, and by whose vibrations light communicates 
heat to bodies, and is put into fits of easy reflectiou 
and transmission. 



HYPOTHESIS OF ETHER. 273 

This ethereal medium, according to our author, is 
exceedingly more rare and more elastic than air. 
It pervades all bodies, and is expanded through all 
the heavens. It is much rarer within the dense 
bodies of the sun, stars, planets, and comets, than 
in the celestial spaces between them, and also more 
rare within glass, water, &c. than in the free and 
open spaces void of air and other grosser bodies. 
In passing out of glass, water, &c. and other dense 
bodies into empty space, it grows denser and denser 
by degrees, and this gradual condensation extends 
to some distance from the bodies. Owing to its 
great elasticity, and, consequently, its efforts to 
spread in all directions, it presses against itself, and, 
consequently, against the solid particles of bodies, 
so as to make them continually approach to one 
another, the body being impelled from the denser 
parts of the medium towards the rarer with all that 
power which we call gravity. 

In employing this medium to explain the nature 
of light, Newton does not suppose, with Descartes, 
Hooke, Huygens, and others, that light is nothing 
more than the impression of those undulations on 
the retina. He regards light as a peculiar substance, 
composed of heterogeneous particles thrown off with 
great velocity, and in all directions, from luminous 
bodies ; and he supposes that these particles while 
passing through the ether, excite in it vibrations or 
pulses which accelerate or retard the particles of 
light, and thus throw them into their alternate fits 
of easy reflection and transmission. 

Hence, if a ray of light falls upon a transparent 
body, in which the ether consists of strata of varia- 
ble density, the particles of light acted upon by the 
vibrations which they create will be urged with an 
accelerated velocity in entering the body, while their 
velocity will be retarded in quitting it. In this man- 
ner he conceives the phenomena of refraction to be 
produced, and he shows how in such a case the 



274 SIR ISAAC NEWTON. 

refraction would be regulated by the law of the* 
sines. 

In order that the ethereal medium may produce 
the fits of easy reflection and transmission, he con- 
ceives that its vibrations must be swifter than light. 
He computes its elasticity to be 490,000,000,000 
times greater than that of air, in proportion to its 
density, and about 600,000,000 times more rare than 
water, from which he infers that the resistance 
which it would oppose to the motions of the planets 
would not be sensible in 10,000 years. He considers 
that the functions of vision and hearing may be per- 
formed chiefly by the vibrations of this medium, 
executed in the bottom of the eye, or in the auditory 
nerve by the rays of light, and propagated through 
the 'solid, pellucid, and uniform capillamenta of the 
optic or auditory nerves into the place of sensation ; 
and he is of opinion that animal motion may be 
performed by the vibrations of the same medium, 
excited in the brain by the power of the will, and 
propagated from thence by the solid, pellucid, and 
uniform capillamenta of the nerves into the muscles 
for contracting and dilating them. 

In the registers of the Royal Society there exist 
several letters* on the excitation of electricity in 
glass, which were occasioned by an experiment of 
this kind having been mentioned in Sir Isaac's 
hypothesis of light. The society had ordered the 
experiment to be tried at their meeting of the 16th 
December, 1675 ; but, in order to secure its success, 
Mr. Oldenburg wrote to Sir Isaac for a more par- 
ticular account of it. Sir Isaac being tnus "put 
upon recollecting himself a little farther about it," 
remembers that he made the experiment with a 
glass fixed at the distance of the ^d of an inch from 
one end of a brass hoop, and only the ^th of an inch 
from the other. Small pieces of thin paper were 

* See Newtoni Opera, by Horsley, vol. iv. p. 375-382 



REFLECTING SEXTANT. 275 

then laid upon the table ; when the glass was laid 
above them and rubbed, the pieces of paper leaped 
from the one part of the glass to the other, and 
twirled about in the air. Notwithstanding tin's ex-] 
plicit account of the experiment, it entirely failed 
at the Royal Society, and the secretary was de- 
sired to request the loan of Sir Isaac's apparatus,' 
and to inquire whether or not he had secured the 
papers from being moved by the air, which might 
have somewhere stole in. In a letter, dated 21st 
December, Sir Isaac recommended to the society to 
rub the glass " with stuff whose threads may rake 
its surface, and, if that will not do, to rub it with 
the fingers' ends to and fro, and knock them as 
often upon the glass." These directions enabled 
the society to succeed with the experiment on the 
13th January, 1676, when they used a scrubbing 
brush of short hog's bristles, and the heft of a knife 
made with whalebone. 

Among the minor inventions of Sir Isaac Newton, 
we must enumerate his reflecting instrument for 
observing the moon's distance from the fixed stars 
at sea. The description of this instrument was com- 
municated to Dr. Halley in the year 1700 ; but, either 
from having mislaid the manuscript, or from attach- 
ing no value to the invention, he never communi- 
cated it to the Royal Society, and it remained among 
his papers till after his death in 1742, when it was 
published in the Philosophical Transactions. The 
following is Sir Isaac's own description of it as 
communicated to Dr. Halley. 

" In the annexed figure PQRS denotes a plate of 
brass, accurately divided in the limb DQ, into J de- 
grees, i minutes, and ~ minutes, by a diagonal 
scale ; and the i degrees, and minutes, and -~ 
minutes, counted for degrees, minutes, and j minutes. 
AB is a telescope three or four feet long, fixed on 
the edge of that brass plate. G is a speculum fixed 



276 



SIR ISAAC NEWTON. 



on the brass plate perpendicularly as near as 
may be to the object-glass of the telescope, so as 

Fig. 12. 




to be inclined forty-five degrees to the axis of 
the telescope, and intercept half the light which 
would otherwise come through the telescope to the 
eye. CD is a moveable index turning about the 
centre C, and, with its fiducial edge, showing the 
degrees, minutes, and % minutes on the limb of the 
brass plate PQ ; the centre C must be over against 
the middle of the speculum G. H is another specu- 
lum, parallel to the former, when the fiducial edge 
of index falls on 0' 0" ; so that the same star may 
then appear through the telescope in one and the 
same place, both by the direct rays and by the re- 
flexed ones ; but if the index be turned, the star shall 
appear in two places, whose distance is showed on 
the brass limb by the index. 

"By this instrument the distance of the moon 
from any fixed star is thus observed : view the star 



REFLECTING MICROSCOPE. 277 

through the perspicil by the direct light, and the 
moon by the reflexed (or on the contrary); and 
turn the index till the star touch the limb of the 
moon, and the index shall show on the brass limb 
of the instrument the distance of the star from the 
moon's limb ; and though the instrument shake by 
the motion of the ship at sea, yet the moon and star 
will move together as if they did really touch one 
another in the heavens ; so that an observation may 
be made as exactly at sea as at land. 

" And by the same instrument may be observed 
exactly the altitudes of the moon and stars, by 
bringing them to the horizon ; and thereby the lati- 
tude and times of observation may be determined 
more exactly than by the ways now in use. 

" In the time of the observation, if the instrument 
move angularly about the axis of the telescope, the 
star will move in a tangent of the moon's limb, or 
of the horizon ; but the observation may notwith- 
standing be made exactly, by noting when the line 
described by the star is a tangent to the moon's 
limb, or to the horizon. 

"To make the instrument useful, the telescope 
ought to take in a large angle ; and to make the 
observation true, let the star touch the moon's limb, 
not on the outside, but on the inside." 

This ingenious contrivance is obviously the very 
same invention as that which Mr. Hadley produced 
in 1731, and which, under the name oif Hadley's 
Quadrant, has been of so great service in navigation. 
The merit of its first invention must therefore be 
transferred to Sir Isaac Newton. 

In the year 1672, Sir Isaac communicated to 
Mr. Oldenburg his design for a microscope, which 
he considered to be as capable of improvement as 
the telescope, and perhaps more so, because it 
requires only one speculum. This microscope is 
shown in the annexed diagram, where AB is the 
object-metal, CD the eye-glass, F their common 
Aa 



278 SIR ISAAC NEWTON. 

focus, and the other focus of the metal in which 
the object is placed. This ingenious idea has been 

Fig. 13. 




greatly improved in modern times by Professor 
Amici, who makes AB a portion of an ellipsoid, 
whose foci are O and F, and who places a small 
plain speculum between O and AB, in order to re- 
flect the object, which is placed on one side AP, for 
the purpose of being illuminated. 

In another letter to Mr. Oldenburg, dated July 
llth in the same year, he suggests another improve- 
ment in microscopes, which is to "illuminate the 
object in a darkened room with the light of any 
convenient colour not too much compounded : for 
by that means the microscope will, with distinct- 
ness, bear a deeper charge and larger aperture, 
especially if its construction be such as I may here- 
after describe."* This happy idea I have some 
years ago succeeded in realizing, by illuminating 
microscopic objects with the light of a monochro- 
matic lamp, which discharges a copious flame of 
pure yellow light of definite refrangibility.f 

In order to remedy the evils arising from the 
weak reflecting power of speculum metal, and from 
its tarnishing by exposure to the air, Sir Isaac pro- 
posed to substitute for the small oval speculum a 
triangular prism of glass or crystal ABC. Its side 

* Sir Isaac does not seem to have afterward described this construe 
tion. 

t See Edinburgh Transactions, vol. ix. p. 433, and the Edinburgh 
Journal of Science, July, 1829, No. I. New Series, p. 108. 



PRISMATIC REFLECTOR. 



279 



AB fa he supposes to perform the office of that metal, 
by reflecting towards the eye-glass the light which 
comes from the concave speculum DF, fig. 13, 
whose light he supposes to enter into this prism at 
its side CB be, and lest any colours should be pro^ 
duced by the refraction of these planes, it is requisite 
that the angles of the 
prism at Aa and B& be 
precisely equal. This 
maybe done most conve- 
niently, by making them 
half right angles, and con- 
sequently the third angle 
at Cc a right one. The 
plane AB la will reflect 
all the light incident upon 
it ; but in order to ex- 
clude unnecessary light, 
it will be proper to cover 
it all over with some black substance excepting two 
circular spaces of the planes -Ac and Be, through 
which the useful light may pass. The length of the, 

Fig. 15 





prism should be such that its 
be square, and so much of the 



Ac and Be may 
B and b as are 



SIR ISAAC NEWTON. 

superfluous ought to be ground off, to give passage 
for as much light as is possible from the object to 
the speculum. 

One great advantage of this prism, which cannot 
be obtained from the oval metal, is, that without 
using two glasses the object may be erected, and 
the magnifying power of the telescope varied at 
pleasure, by merely varying the distances of the 
speculum, the prism, and the eye-glass. This will 
be understood from Jig. 16, where AI represents 

Fig. 16. 




the great concave speculum, EF the eye-glass, and 
BCD the prism of glass, whose sides BC and CD 
are not flat, but spherically convex. The rays which 
come from G, the focus of the great speculum AI, 
will, by the refraction of the first side BC, be re- 
duced to parallelism, and after reflection from the 
base CD, will be made by the refraction of the next 
side BD to converge to the focus H of the eye-glass 
EF. If we now bring the prism BCD nearer the 
image at G, the point H will recede from BD, and 
the image formed there will be greater than that at 
G, and if we remove the prism BCD from G, the 
point H will approach to BD, and the image at H 



IMPRESSIONS ON THE RETINA. 

will be less than that at G. The prism BCD per- 
forms the same part as a convex lens, G and H 
being its conjugate foci, and the relative size of the 
images formed at these points being proportional to 
their distance from the lens. This construction 
would be a good one for varying optically the angu- 
lar distance of a pair of wires placed in the focus of 
. the eye-glass EF ; and by bisecting the lenticular 
, prism BCD, and giving the halves a slight inclina- 
; tion, we should be able to separate and to close the 
two images or disks which would thus be produced, 
and thus -form a double image micrometer. 

Among the minor and detached labours of Sir 
Isaac, we must not omit his curious experiments on 
the action of light upon the retina. Locke seems 
to have wished his opinion respecting a fact stated 
in Boyle's Book on Colours, and in a letter from 
Cambridge, dated June 30th, 1691, he communicated 
to his friend the following very remarkable obser- 
vations made by himself. 

" The observation you mention in Mr. Boyle's 
book of colours I once made upon myself with the 
hazard of my eyes. The manner was this ; I looked 
a very little while upon the sun in the looking-glass 
with my right eye, and then turned my eyes into a 
dark corner of my chamber, and winked, to observe 
the impression made, and the circles of colours 
which encompassed it, and how they decayed by 
degrees, and at last vanished. This I repeated a 
second and a third time. At the third time, when 
the phantasm of light and colours about it were 
almost vanished, intending my fancy upon them to 
see their last appearance, I found, to my amaze- 
ment, that they began to return, and by little and 
little to become as lively and vivid as when I had 
newly looked upon the sun. But when I ceased to 
intend my fancy upon them, they vanished again. 
After this, I found, that as often as I went into the 
dark, and intended my mind upon them, as wheo 
Aa2 



282 SIR ISAAC NEWTON. JR 

a man lobks earnestly to see any thing which is 
difficult to be seen, I could make the phantasm re- 
turn without looking any more upon the sun ; and 
the oftener I made it return, the more easily I could 
make it return again. And at length, by repeating 
this without looking any more upon the sun, I made 
such an impression on my eye, that, if I looked upon 
the clouds, or a book, or any bright object, I saw 
upon it a round bright spot of light like the sun, 
and, which is still stranger, though I looked upon 
the sun with my right eye only, and not with my. 
left, yet my fancy began to make an impression, 
upon my left eye, as well as upon my right. For if 
I shut my right eye, or looked upon a book or the 
clouds with my left eye, I could see the spectrum 
of the sun almost as plain as with my right eye, if I 
did but intend my fancy a little while upon it ; for 
at first, if I shut my right eye, and looked with my 
left, the spectrum o'f the sun did not appear till I in- 
tended my fancy upon it ; but by repeating, this ap- 
peared every time more easily. And now, in a few 
hours' time, I had brought my eyes to such a pass, 
that I could look upon no bright object with either 
eye but I saw the sun before me, so that I durst 
neither write nor read ; but to recover the use of my 
eyes, shut myself up in my chamber made dark, for 
three days together, and used all means to divert 
my imagination from the sun. For if I thought 
upon him, I presently saw his picture, though I was 
in the dark. But by keeping in the dark, and em- 
ploying my mind about other things, I began in 
three or four days to have some use of my eyes 
again ; and, by forbearing to look upon bright ob- 
jects, recovered them pretty well, though not so 
well but that, for some months after, the spectrum 
Df the sun began to return as often as I began to 
meditate upon tha phenomena, even though I lay in 
bed at midnight with my curtains drawn. But now ( 
I have been very well for many years, though I am 



IMPRESSIONS ON THE RETINA. 283 

apt to think, if I durst venture my eyes, I could still 
make the phantasm return by the power of my 
fancy. This story I tell you, to let you understand, 
that in the observation related by Mr. Boyle, the 
man's fancy probably concurred with the impression 
made by the sun's light to. produce that phantasm 
of the sun which he constantly saw in bright objects. 
And so your question aboutthe cause of this phan- 
tasm involves another about the power of fancy, 
which I must confess is too hard a knot for me to 
untie. To place this effect in a constant motion is 
hard, because the sun ought then to appear per- 
petually. It seems rather to consist in a disposition 
of the sensorium to move the imagination strongly, 
and to be easily moved, both by the imagination 
and by the light, as often as bright objects are looked 
upon." 

These observations possess in many respects a high 
degree of interest. The fact of the transmission 
of the impression from the retina of the one eye to 
that of the other is particularly important ; and it 
deserves to be remarked, as a singular coincidence, 
that I had occasion to observe and to describe the 
same phenomena above twenty years ago,* and long 
oefore the observations of Sir Isaac were commu- 
nicated to the scientific world. 

* Art. Accidental Colour* in the Edinburgh Encyclopedia. 



284 SIR ISAAC NEWTON 



CHAPTER XVIII. 

His Acquaintance, with Dr. Pemberton, who edits the Third Edition of 
the Principia His Jirst Attack of ill Health His Recovery- He is 
taken ill in consequence of attending the Royal Society His Death 
on the 20th March, 1727 His Body lies in state His FuneralHe 
is. buried in Westminster Abbey His Monument described His Epi- 
taph A Medal struck in honour of him Roubiliac's full-length 
Statue of him erected in Cambridge Division of his Property His 
Successors. 

ABOUT the year 1722, Sir Isaac was desirous of 
publishing a third edition of his Principia, and the 
premature death of Mr. Cotes having deprived him 
of his valuable aid, he had the good fortune to be- 
come acquainted with Dr. Henry Pemberton, a young 
and accomplished physician, who had cultivated 
mathematical learning with considerable success. 
M. Poleni, an eminent professor in the University 
of Padua, having endeavoured, on the authority of 
a new experiment, to overturn the common opinion 
respecting the force of bodies in motion, and to es- 
tablish that of Leibnitz in its place, Dr. Pemberton 
transmitted to Dr. Mead a demonstration of its 
inaccuracy. Dr. Mead communicated this paper to 
Sir Isaac, who not only highly approved of it, but 
added a demonstration of his own, drawn from 
another consideration of the subject ; and this was 
printed without his name, as a postscript to Pem- 
berton's paper, when it appeared in the Transac- 
tions.* 

In a short time after the commencement of their 
acquaintance, Sir Isaac engaged Dr. Pemberton to 
superintend the new edition of the Principia. In 
discharging this duty, Dr. Pemberton had occasion 
to make many remarks on this work, which Sir Isaac 

* Bee Phil. Trans. 1722, vol. xxxiii. p. 57. 



ILL HEALTH. 285 

always received with the utmost goodness, and the 
new edition appeared with numerous alterations in 
1726. On the occasions upon which he had per- 
sonal intercourse with Sir Isaac, and which were 
necessarily numerous, he endeavoured to learn his 
opinions on various mathematical subjects, and to 
obtain some historical information respecting his 
inventions and discoveries. Sir Isaac entered freely 
into all these topics ; and during the conversations 
which took place, and while they were reading 
together Dr. Pemberton's popular account of Sir 
Isaac's discoveries, he obtained the most perfect 
evidence that, though his memory was much de- 
cayed, yet he was fully able to understand his own 
writings. 

During the last twenty years of his life, which he 
spent in London, the charge of his domestic con- 
cerns devolved upon his beautiful and accomplished 
niece, Mrs. Catharine Barton, the wife of Colonel 
Barton, for whom, as we have already seen, the 
Earl of Halifax had conceived the warmest affec- 
tion. This lady, who had been educated at her 
uncle's expense, married Mr. Conduit, and continued 
to reside with her husband in Sir Isaac's house till 
the time of his death. 

In the year 1722, when he had reached the 
eightieth year of his age, he was seized with an 
incontinence of urine, which was ascribed to stone 
in the bladder, and was considered incurable. By 
means of a strict regimen, however, and other pre- 
cautions, he was enabled to alleviate his complaint, 
and to procure long intervals of ease. At this time 
he gave up the use of his carriage, and always went 
out in a chair. He declined all invitations to dinner, 
and at his own house he had only small parties. In 
his diet he was extremely temperate. Though he 
took a little butcher meat, yet the principal articles 
of his food were broth, vegetables, and fruit, of 
which he always ate very heartily. In spite of all 



286 SHI ISAAC NEWTON. 

his precautions, however, he experienced a return 
of his old complaint, and in August, 1724, he passed 
a stone the size of a pea, which came away in two 
pieces, the one at the distance of two days from the 
other. After some months of tolerable good health, 
he was seized in January, 1725, with a violent cough 
and inflammation of the lungs ; and in consequence 
of this attack, he was prevailed upon, with some 
difficulty, to take up his residence at Kensington, 
where his health experienced a decided improve- 
ment. In February, 1725, he was attacked in both 
his feet with a fit of the gout, of which he had re- 
ceived a slight warning a few years before, and the 
effect of this new complaint was to produce a great 
and beneficial change in his general health. On 
Sunday the 7th March, when his head was clearer 
and his memory stronger than Mr. Conduit had 
known it to be for some time, he entered into a long 
conversation on various subjects in astronomy. He 
explained to Mr. Conduit how comets might be 
formed out of the light of vapours discharged from 
the sun and the fixed stars as the centres of sys- 
tems. He conceived that these luminaries were 
replenished by the same comets being again returned 
to them ; and upon this principle he explained the 
extraordinary lights which were seen among the 
fixed stars by Hipparchus, Tycho Brahe, and Kepler's 
disciples, and which he supposed to arise from the 
additional fuel which they received.* 

Notwithstanding the improvement which his health 
had experienced, his indisposition was still suffi- 
ciently severe to unfit him for the discharge of his 
duties at the mint ; and as his old deputy was con- 
fined with the dropsy, he was desirous in 1725 of 
resigning his office to Mr. Conduit. Difficulties 
probably were experienced in making this arrange- 
ment, but his nephew discharged for him all the 

* This conversation, originally copied from Mr. Conduit's handwriting, 
Ui given in the Appendix, No. iii. p. 320. 



DEATH. 287 

duties of his office ; and during the last year of his 
life he hardly ever went to the mint. 

But though every kind of motion was calculated 
to aggravate his complaint, and though he had de- 
rived from absolute rest and from the air at Ken- 
sington the highest benefit, yet great difficulty was 
experienced in preventing him from occasionally 
going to town. Feeling himself able for the jour- 
ney, he went to London on Tuesday the 28th of 
February, 1727, to preside at a meeting of the Royal 
Society. On the following day Mr. Conduit con- 
sidered him better than he had been for many years, 
and Sir Isaac was himself so sensible of this im- 
provement in his health, that he assured his nephew 
that on the Sunday preceding, he had slept from 
eleven o'clock at night till eight o'clock next morn- 
ing without waking. He had undergone, however, 
great fatigue in attending the meeting of the Royal 
Society, and in paying and receiving visits, and the 
consequence of this was a violent return of his 
former complaint. He returned to Kensington on 
Saturday the 4th March, and was attended by Dr. 
Mead and Dr. Cheselden, who pronounced his dis- 
ease to be stone, and held out no hopes of his 
recovery. From the time of his last journey to 
London he had experienced violent fits of pain with 
very short intermissions ; and though the drops of 
sweat ran down his face during these severe parox- 
ysms, yet he never uttered a cry or a complaint, or 
displayed the least marks of peevishness or impa- 
tience ; but during the short intervals of relief which 
occurred, he smiled and conversed with his usual 
gayety and cheerfulness. On Wednesday the 15th 
of March he seemed a little better; and slight, 
though groundless hopes were entertained of his 
recovery. On the morning of Saturday the 18th 
he read the newspapers, and carried on a pretty long 
conversation with Dr. Mead, when all his senses and 
faculties were strong and vigorous ; but at six o'clock 

1 1 \ i i in I in i m 



288 SIR ISAAC NEWTON. 

of the same evening he became insensible, and he 
continued in that state during the whole of Sunday, 
and till Monday the 20th, when he expired between 
one and two o'clock in the morning, in the eighty- 
fifth year of his age. 

His body was removed from Kensington to Lon- 
don, and on Tuesday the L8th March it lay in state 
in the Jerusalem Chamber, and was thence conveyed 
to Westminster Abbey, where it was buried near the 
entrance into the choir on the left-hand. The pall 
was supported by the Lord High Chancellor, the 
Dukes of Roxburghe and Montrose, and the Earls 
of Pembroke, Sussex, and Macclesfield, who were 
Fellows of the Royal Society. The Hon. Sir Mi- 
chael Newton, Knight of the Bath, was chief 
mourner, and was followed by some other relations, 
and several distinguished characters who were inti- 
mately acquainted with the deceased. The funeral 
service was performed by the Bishop of Rochester, 
attended by the prebend and choir. 

Sensible of the high honour which they derived 
from their connexion with so distinguished a phi- 
losopher, the relations of Sir Isaac Newton who 
inherited his personal estate,* agreed to devote 500/ 
to the erection of a monument to his memory, and 
the dean and chapter of Westminster appropriated 
for it a place in the most conspicuous part of the 
Abbey, which had often been refused to the greatest 
of our nobility. This monument was erected in 
1731. On the front of a sarcophagus resting on a 
pedestal are sculptured in basso-relievo youths bear- 
ing in their hands the emblems of Sir Isaac's prin- 
cipal discoveries. One carries a prism, another a 
reflecting telescope, a third is weighing the sun and 

* These were the three children of his half-brother Smith, the three 
children of his half-sister Pilkington, and the two daughters of his half- 
sister Barton, all of whom survived Sir Isaac. New Anecdotes of Sir 
Isaac Newton, by J. H., a Gentleman of his Mother's Family. See An 
nual Register, 1776, vol. xix. p. 25 of Characters, The author of thia 
paper was James Hutton, Esq. of Pimlico. 

? f !! ; { I > 



MONUMENT. 289 

planets with a steelyard, a fourth is employed about 
a furnace, and two others are loaded with money 
newly coined. On the sarcophagus is placed the 
figure of Sir Isaac in a cumbent posture, with his 
elbow resting on several of his works. Two youths 
stand before him with a scroll, on which is drawn a 
remarkable diagram relative to the solar system, and 
above that is a converging series. Behind the sar- 
cophagus is a pyramid, from the middle of which 
rises a globe in mezzo-relievo, upon which several 
of the constellations are drawn, in order to show 
the path of the comet of 1681, whose period Sir 
Isaac had determined, and also the position of the 
solstitial colure mentioned by Hipparchus, and by 
means of which Sir Isaac had, in his Chronology, 
fixed the time of the Argonautic expedition. A figure 
of 'Astronomy as Queen of the Sciences sits weep- 
ing on the Globe with a sceptre in her hand, and a 
star surmounts the summit of the pyramid. The 
following epitaph is inscribed on the monument. 

Hie situs est 

Isaacus Newton, Eques Auratus, 

Qui Animi Vi prope divina, 

Planetarum Motus, Figuras, 

Cometarum Semitas, Oceanique JEstus, 

Sua Mathesi facem preferente, 

Primus demon stravit. 

Radiorum Lucis dissimilitudines, 

Colorumque inde nasceniium Proprietates, 

Quas nemo aniea vel suspicatus erat, pervestigavit, 

Naturae, Antiquitates, S. Scriptures, 

Sedulus, sagax, fidus Interpres, 
Dei Opt. Max. Majestatem Philosophia asseruit, 

Evangelii simplicitatem moribus expressit. 
Sibi gratulentur Mortales, tale tantumque extitisse, 

HUMANI GENERIS DECUS. 

Natus xxv. Decemb. MDCXL1I. Obiit. xx. Mar. 

MDCCXXVII. 

Of which the following is a literal translation : 

Here lies 

Isaac Newton, Knight, 
Who, by a Vigour of Mind almost supernatural, 

First demonstrated 
The Morions and Figures of the Planets, 

Bb 



290 SIR ISAAC 

The Paths of the Comets, and the Tides of the Ocean 

He diligently investigated 

The different Re fr eligibilities of the Rays of Light, 

And the Properties of the Colours to which they give rise. 

AM assiduous, sagacious, and faithful Interpreter 

Of Nature, Antiquity, and the Holy Scriptures, 

He asserted in his Philosophy the Majesty of God, 

And exhibited in his conduct the Simplicity of the Gospel. 

Let Mortals rejoice 
That there has existed such and so great 

AN OKNAMENT op- HFMAN NATTHE. 
Born 25th Dec. 1642, Died 20th March, 1727. 

In the beginning of 1731, a medal was struck 'at 
the Tower in honour of Sir Isaac Newton. It had 
on one side the head of the philosopher, with the 
motto, Felix cognoscere causas, and on the reverse a 
figure representing the mathematics. 

On the 4th February, 1755, a magnificent full- 
length statue of Sir Isaac Newton in white marble 
was erected in the antechapel of Trinity College. 
He is represented standing on a pedestal in a loose 
gown, holding a prism, and looking upwards with an 
expression of the deepest thought. On the pedestal 
is the inscription, 

Qui genus humanum ingenio superavit. 
Who surpassed all men in genius. 

This statue, executed by Roubiliac, was erected 
at the expense of Dr. Robert Smith, the author of 
the Compleat System of Optics, and professor of as- 
tronomy and experimental philosophy at Cambridge. 
It has been thus described by a modern poet : 

Hark where the organ, full and clear, 
With loud hosannas charms the ear; 
Behold, a prism within his hands, 
Absorbed in thought great Newton stands 
Such was his brow, and looks serene, 
His serious gait and musing mien, 
When taught on eagle wings to fly, 
He traced the wonders of the sky ; 
The chambers of the sun explored, 
Where tints of thousand hues were stored. 

pr. Smith likewise bequeathed the sum of 500/. 



PROPERTY SUCCESSORS. 291 

for executing a painting on glass for the window at 
the south end of Trinity College, Cambridge. The 
subject represents the presentation of Sir Isaac 
Newton to his majesty George III., who is seated 
under a canopy with a laurel chaplet in his hand, and 
attended by the British Minerva, apparently advising 
him to reward merit in the person of the great phi- 
losopher. Below the throne, the Lord Chancellor 
Bacon is proposing to register the reward about to 
be conferred upon Sir Isaac. The original drawing 
of this absurd picture was executed by Cypriani, 
and cost one hundred guineas. 

The personal estate of Sir Isaac Newton, which 
was worth about 32,000/., was divided among his 
four nephews and four nieces of the half-blood, the 
grandchildren of his mother by the Reverend Mr. 
Smith. The family estates of Woolsthorpe and 
Sustern he bequeathed to John Newton, the heir-at- 
law, whose great-grandfather was Sir Isaac's uncle. 
This gentleman does not seem to have sufficiently 
valued the bequest, for he sold them in 1732, to Ed- 
mund Turnor of Stoke Rocheford.* A short time 
before his death, Sir Isaac gave away an estate in 
Berkshire to the sons and daughter of a brother of 
Mrs. Conduit, who, in consequence of their father 
dying before Sir Isaac, had no share in the personal 
estate ; and he also gave an estate of the same value, 
which he bought at Kensington, to Catharine, the 
only daughter of Mr. Conduit, who afterward mar- 
ried Mr. Wallop, the eldest son of Lord Lymington. 
This lady was afterward Viscountess Lymington, 
and the estate of Kensington descended to the late 
Earl of Portsmouth, by whom it was sold. Sir Isaac 
was succeeded as master and warden in the mint by 
his nephew, John Conduit, Esq., who wrote a trea- 
tise on the gold and silver coin, and who died in 
1737, leaving behind him his wife and daughter, the 
Dormer of whom died in 1739, in the 59th year of 
her age. 

* Tunwr's Collections^ &c. p. 158. See APPENDIX, P 3 J 6' 



292 SIR ISAAC NEWTON 



CHAPTER XIX. 

Permanence of Newton's Reputation Character of his Genius His 
Methods of Investigation similar to that used by Galileo Error in 
ascribing his Discoveries to the Use of the Methods recommended by 
Lord Bacon The Pretensions of the Baconian Philosophy examined 
Sir Isaac Newton' s social Character His great Modesty The 
Simplicity of his Character His religious and moral Character 
His Hospitality and Mode of Life His Generosity and Charity 
His Absence His personal "Appearance Statues and Pictures of 
him Memorials and Recollections of him. 

SUCH were the last days of Sir Isaac Newton, and 
such the last laurels which were shed over his grave. 
A century of discoveries has since his day been 
added to science ; but brilliant as these discoveries 
are, they have not obliterated the minutest of his 
labours, and have served only to brighten the halo 
which encircles his name. The achievements of 
genius, like the source from which they spring, are 
indestructible. Acts of legislation and deeds of war 
may confer a high celebrity, but the reputation which 
they bring is only local and transient; and while 
they are hailed by the nation which they benefit, 
they are reprobated by the people whom they ruin ? 
or enslave. The labours of science, on the contrary, 
bear along with them no counterpart of evil. They 
are the liberal bequests of great minds to every 
individual of their race, and wherever they are wel- 
comed and honoured they become the solace of 
private life, and the ornament and bulwark of the 
commonwealth. 

The importance of Sir Isaac Newton's discoveries 
has been sufficiently exhibited in the preceding 
chapters : the peculiar character of his genius, and 
the method which he pursued in his inquiries, can 
be gathered only from the study of his works, and 



CHARACTER OF HIS GENIUS. 293 

From the history of his individual labours. Were 
we to judge of the qualities of his mind from the 
early age at which he made his principal discoveries, 
and from the rapidity of their succession, we should 
^e led to ascribe to him that quickness of penetra- 
tion, and that exuberance of invention, which is 
more characteristic of poetical than of philosophical 
jehius. But we must recollect that Newton was 
Placed in the most favourable circumstances for the 
development of his powers. The flower of his 
youth and the vigour of his manhood were entirely 
levoted to science. No injudicious guardian con- 
;rolled his ruling passion, and no ungenial studies or 
)rofessional toils interrupted the continuity of his 
mrsuits. His discoveries were, therefore, the fruit 
of persevering and unbroken study; and he himself 
declared, that whatever service he had done to the 
public was not owing to any extraordinary sagacity, 
)ut solely to industry and patient thought. 

Initiated early into the abstractions of geometry, 
le was deeply imbued with her cautious spirit ; and 
f his acquisitions were not made with the rapidity 
of intuition, they were at least firmly secured ; and 
;he grasp which he took of his subject was propor- 
lonal to the mental labour which it had exhausted. 
Overlooking what was trivial, and separating what 
was extraneous, he bore down with instinctive 
sagacity on the prominences of his subject, and 
laving thus grappled with its difficulties, he never 
Bailed to intrench himself in its strongholds. 

To the highest powers of invention Newton 
added, what so seldom accompanies them, the talent 
of simplifying and communicating his profoundest 
speculations.* In the economy of her distributions, 
nature is seldom thus lavish of her intellectual gifts 
The inspired genius which creates is rarely eon- 

* This valuable faculty characterizes all his writings, whether theo- 
logical, chymical, or mathematical ; but it is peculiarly displaced 4fl hit 
treatise on Universal Arithmetic, and in his Optical Lectures. 



294 SIR ISAAC NEWTON. 

ferred along with the matured judgment which 
combines, and yet without the exertion of both the 
fabric of human wisdom could never have been 
reared. Though a ray from heaven kindled the 
vestal fire, yet an humble priesthood was required to 
keep alive the flame. 

The method of investigating truth by observation 
and experiment, so successfully pursued in the Prin- 
cipia, lias been ascribed by some modern writers of 
great celebrity to Lord Bacon ; and Sir Isaac New- 
ton is represented as having owed all his discoveries 
to the application of the principles of that distin- 
guished writer. One of the greatest admirers of 
Lord Bacon has gone so far as to characterize him 
as a man who has had no rival in the times which 
are past, and as likely to have none in those which 
are to come. In a eulogy so overstrained as this, 
we feel that the language of panegyric has passed 
into that of idolatry ; and we are desirous of weigh- 
ing the force of arguments which tend to depose 
Newton from the high-priesthood of nature, and to 
unsettle the proud destinies of Copernicus, Galileo, 
and Kepler. 

That Bacon was a man of powerful genius, and 
endowed with varied and profound talent, the most 
skilful logician, the most nervous and eloquent 
writer of the age which he adorned, are points which 
have been established by universal suffrage. The 
study of ancient systems had early impressed him 
with the conviction that experiment and observation 
were the only sure guides in physical inquiries ; 
and, ignorant though he was of the methods, the 
principles, and the details of the mathematical 
sciences, his ambition prompted him to aim at the 
construction of an artificial system by which the 
laws of nature might be investigated, and which 
might direct the inquiries of philosophers in every 
future age. The necessity of experimental research, 
and of advancing gradually from the study of facts 



BACONIAN PHILOSOPHY. 295 

,0 the determination of their cause, though the 
5To~undwork of Bacon's method, is a doctrine which 
was not only inculcated but successfully followed 
Dy preceding philosophers. In a letter from Tycho 
Brahe to Kepler, this industrious astronomer urges 
us pupil " to lay a solid foundation for his views 
>y actual observation, and then by ascending from 
hese to strive to reach the causes of things ;" and 
t was no doubt under the influence of this advice 
hat Kepler submitted his wildest fancies to the test 
f observation, and was conducted to his most 
plendid discoveries. The reasonings of Corjejjii- x 
us, who preceded Bacon by more than a century, 
Were all founded upon the most legitimate induction. 
}r. Gilbert had exhibited in his treatise on" the ; 
agnet* the most perfect specimen of physical re- 
earch. Leonardo da Vinci had described in the 
learest manner the proper method of philosophical 
nvestigation ;f and the whole scientific career of 
Galileo was one continued example of the most 

* De Magnet e, p. 42, 52, 169, and Pref. p. 30. 

t The following passages from Leonardo da Vinci are very striking : 

" Theory is the general, and practice the soldiers. 

" Experiment is the interpreter of the artifices of nature. It never 
eceives us ; it is our judgment itself which sometimes deceives us, be- 
duse we expect from it effects which are contrary to experiment. We 
nust consult experiment by varying the circumstances till we have 
educed from it general laws ; for it is it which furnishes true laws. 

" In the study of the sciences which depend on mathematics, those 
rtio do not consult nature, but authors, are not the children of nature ; 
ley are only her grandchildren. Nature alone is the master of true 
enius. 

"In treating any particular subject, I would first of all make some 
xperiments, because my design is first to refer to experiment, and then 

demonstrate why bodies are constrained to act in such a manner. 

his is the method which we ought to follow in investigating the phe- 

omena of nature. It is very true that nature begins by reasoning and 

nds with experiment ; but it matters not, we must take the opposite 

ourse; as I have said, we must begin by experiment, and endeavour 

y its means to discover general principles " Thus, says Ventusi, spoke 

eonarc! a century before Bacon, and thus, we add, did Leonard tell phi- 

osophers all that they required for the proper investigation of general 

aws. See Essai sur Us ozuvrages physico-mathematiques de Leonard 

de Vinci, par J. B. Venturi. Paris, 1799, p. 32, 33, &c. See also Carlo 

Amoretti's Memorie storichs su la vita gli studi e le Opere de Lionardo 

da Vinci. Milano, 1804. 



296 SIR ISAAC NEWTON. 

sagacious application of observation and experiment 
to the discovery of general laws. The names of 
Paracelsus, Van Helmont, and Cardan have been 
ranged in opposition to this constellation of great 
names, and while it is admitted that even they had 
thrown off the yoke of the schools, and had" suc- 
ceeded in experimental research, their credulity and 
their pretensions have been adduced as a proof that 
to the " bulk of philosophers" the method of induc- 
tion was unknown. The fault of this argument con- 
sists in the conclusion being infinitely more general 
than the fact. The errors of these men were not. 
founded on their ignorance, but on their presump- 
tion. They wanted the patience of philosophy and 
not her methods. An excess of vanity, a wayward- 
ness of fancy, and an insatiable appetite for that 
species of passing fame which is derived from eccen- 
tricity of opinion, moulded the reasonings and dis- 
figured the writings of these ingenious men ; and it 
can scarcely admit of a doubt, that, had they lived 
in the present age, their philosophical character 
would have received the same impress from the 
peculiarity of their tempers and dispositions. This 
is an experiment, however, which cannot now be 
made ; but the history of modern science supplies 
the defect, and the experience of every man fur- 
nishes a proof that in the present age there are 
many philosophers of elevated talents and inventive 
genius who are as impatient of experimental re- 
search as Paracelsus, as fanciful as Cardan, and as 
presumptuous as Van Helmont. 

Having thus shown that the distinguished philoso- 
phers who flourished before Bacon were perfect 
masters both of the principles and practice of in-, 
ductive research, it becomes interesting to inquire 
whether or not the philosophers who succejeded 
him acknowledged any obligation to his system, or 
derived the slightest advantage from his precepts. 
If Bacon constructed a method to which modern 



BACONIAN PHILOSOPHY. 297 

cience owes its existence, we shall find its cultiva- 
ars grateful for the gift, and offering the richest 
icense at the shrine of a benefactor whose gene- 
ous labours conducted them to immortality. No 
uch testimonies, however, are to be found. Nearly 
wo hundred years have gone by, teeming with 
le richest fruits of human genius, and no grateful 
isciple has appeared to vindicate the rights of the 
lleged legislator of science. Even Newton, who 
as born and educated after the publication of the 
'ovum Organon, never mentions the name of Bacon !| 
r his system, and the amiable and indefatigable 
oyle treated him with the same disrespectful 
lence. When we are told, therefore, that Newton 
wed all his discoveries to the method of Bacon, 
othing more can be meant than that he proceeded 
i that path of observation and experiment which 
ad been so warmly recommended in the Novum 
rganon ; but it ought to have been added, that the 
ame method was practised by his predecessors, 
lat Newton possessed no secret that was not used 
y Galileo and Copernicus, and that he would 
ave enriched science with the same splendid dis- 
overies if the name and the writings of Bacon had 
ever been heard of. 

From this view of the subject we shall now pro- 

ed to examine the Baconian process itself, and 

onsider if it possesses any merit as an artificial 

lethod of discovery, or if it is at all capable of being 

mployed, for this purpose, even in the humblest 

alks of scientific inquiry. 

The process of Lord Bacon was, we believe, never 

ied by any philosopher but_ himself. As the sub- 

ect ot its application, he selected that of heat. With 

'.s usual erudition, he collected all the facts which 

dence could supply, he arranged them in tables, 

e cross-questioned them with all the subtlety of a 

pleader, he combined them with all the sagacity 

f)f a judge, and he conjured with them by all the 



298 SIR ISAAC NEWTON. 

I magic of his exclusive processes. But, after all thi 
display of physical logic, nature thus interrogate* 
was still silent. The oracle which he had himsel 
established refused to give its responses, and th 
ministering priest was driven with discomfiture fron 
his own shrine. This example, in short, of the ap 
plication of his system, will remain to future age 
as a memorable instance of the absurdity of attempt 
ing to fetter discovery by any artificial rules. 

Nothing even in mathematical science can b< 
more certairTthari~tljat a collection of scientific fact 
are of theniselves^iiicapable of leading to discover}/ 
or to the determinatioif or^iieral Taws, unless lifie] 
'conTaTfn:Ke~ r pre'Jqniihating fact or relation in whicj 
fee discovery mainly resides. A vertical column o 
arch-stones possesses more strength than the sam 
materials arranged in an arch without the key-stone 
However nicely they are adjusted, and however no 
bly the arch may spring, it never can possess eithe 
equilibrium or stability. In this comparison all th< 
facts are supposed to be necessary to the final re 
suit; but, ill the inductive method, it is impossihl< 
to ascertain the relative importance of any facts, o 
even tiyjetermina^ "the Tacts have any value at all 
till the{master-fact^hrcri constitutes the discover 
has crowned the zealous efforts of the aspiring phi 
' losopher. The mind then returns to the dark am 
barren waste over which it has been hovering ; am 
by the guidance of this single torch it embraces 
under the comprehensive grasp of general princi 
pies, the multifarious and insulated phenomena whicl 
had formerly neither value nor connexion. Henc< 
it must be obvious to the most superficial thinker 
that discovery consists either in the detection o: 
some concealed relation some deep-seated affinity 
which baffles ordinary research, or in the discover] 
;of some simple fact which is connected by slende 
ramifications with the subject to be investigated 
but which, when once detected, carries us back fo 



TRUE PROCESS OF INVESTIGATION. 299 

s divergence to all the phenomena which it em- 
races and explains. 

In order to give additional support to these views, 
would be interesting to ascertain the general char- 
ter of the process by which a mind of acknow- 
dged power actually proceeds in the path of suc- 
issful inquiry. The history of science does not 
urnish us with much information on this head, and 
it is to be found at all, it must be gleaned from 
lie biographies of eminent men. Whatever this 
rocess may be in its details, if it has any, there 
annot be the slightest doubt that in its generalities 
t least it is the very reverse of the method of in- 
uction. The impatience of genius spurns the re- 
Taints of mechanical rules, and never will submit 
> the plodding drudgery^, of inductive discipline, 
he discovery of a newHSirtNmfits even a patient 
lind for deliberate inquiry?" Conscious of having 
dded to science what had escaped the sagacity of 
Tmer ages, the ambitious spirit invests its new 
cquisition with an importance which does not be- 
ng to it. He imagines a thousand consequences 
i flow from his4iscover$: he forms innumerable 
leories to explaiii^itrana he exhausts his fancy in 
ying all its possible relations to recognised diffi- 
alties and unexplained facts. The reins, however, 
ms freely given to his imagination, are speedily 
rawn up. His wildest conceptions are all subjected 
the rigid test of experiment, and he has thus been 
urried by the excursions of his own fancy into new 
nd fertile paths, far removed from ordinary obser- 
,tion. Here the peculiar character of his own ge- 
us displays itself by the invention of methods of 
ying his own speculations, and he is thus often led 
new discoveries far more important and general 
an that by which he began his inquiry. For a 
nfirmation of these views, we may refei to the 
istory of Kepler's Discoveries ; and if we do not j 
recognise them to the same extent hi the labours of 

I 



300 SIR ISAAC NEWTON. 

I Newton, it is because he kept back his discoverie! 
till they were nearly perfected, and therefore with 
1 held the successive steps of his inquiries. 
>, The social character of Sir Isaac Newton wa? 
such as might have been expected from his intel 
lectual attainments. He was modest, candid, am 
affable, and without any of the eccentricities of ge> 
nius, suiting himself to every company, and speaking 
of himself and others in such a manner that he wai 
never even suspected of vanity. " But this," says 
Dr. Pemberton, " I immediately discovered in him 
which at once both surprised and charmed me* 
Neither his extreme great age nor his universal re* 
putation had rendered him stiff in opinion, or in anj 
degree elated. Of this I had occasion to ha 1 ** 
almost daily experience. The remarks I continual!) 
sent him by letters on the Principia were receivec 
with the utmost goodness. These were so far froir 
being any ways displeasing to him, that on the con- 
trary it occasioned him to speak many kind thing? 
of me to my friends, and to honour me with a public 
testimony of his good opinion." 

The modesty of Sir Isaac Newton in reference tc 
his great discoveries was not founded on any indif- 
ference to the fame which they conferred, or upor 
any erroneous judgment of their importance tc 
science. The whole of his life proves, that he kne\\ 
his place as a philosopher, and was determined tc 
assert and vindicate his rights. His modesty arose 
from the depth and extent of his knowledge, whicl: 
showed him what a small portion of nature he hac 
been able to examine, and how much remained tc 
be explored in the same field in which he had him- 
'self laboured. In the magnitude of the comparisor 
he recognised his own littleness ; and a short time 
before his death he uttered this memorable senti- 
ment : " I do not know what I may appear to the 
world ; but to myself I seem to have been only like 
a boy playing on the seashore, and diverting myself 



SIMPLICITY OF CHARACTER. 301 

in now and then fading a smoother pebble or a pret 
tier shell than ordinary, while the great ocean of 
truth lay all undiscovered before me." What a les- 
son to the vanity and presumption of philosophers, 
to those especially who have never even found the 
smoother pebble or the prettier shell ! What a pre- 
paration for the latest inquiries, and the last views 
of the decaying spirit, for those inspired doctrines 
which alone can throw a light over the dark ocean 
of undiscovered truth ! 

The native simplicity of Sir Isaac Newton's mind 
is finely portrayed in the affecting letter in which 
he acknowledges to Locke that he had thought and 
spoken of him uncharitably ; and the humility and 
candour in which he asks forgiveness could have 
emanated only from a mind as noble as it was pure. 

In the religious and moral character of our author 
there is much to admire and to imitate. While he 
exhibited in his life and writings an ardent regard 
for the general interests of religion, he was at the 
same time a firm believer in revelation. He was 
too deeply versed in the Scriptures, and too much 
imbued with their spirit, to judge harshly of other 
men who took different views of them from himself. 
He cherished the great principles of religious tole- 
ration, and never scrupled to express his abhorrence 
persecution, even in its mildest form. Immo- 
rality and impiety he never permitted to pass unre- 
proved ; and when Dr. Halley* ventured to say any 
thing disrespectful to religion, he invariably checked 
him, and said, " I have studied these things, you 
have not."f 

After Sir Isaac Newton took up his residence in 
London, he lived in a very handsome style, and kept 
his carriage, with an establishment of three male 

* Mr. Hearne, in a memorandum dated April 4th, 1726, states, that a 
great quarrel happened between Sir Isaac Newton and Mr. Halley. If 
this is true, the difference is likely to have originated in Halley's impiety. 

* Professor Rigaud of Oxford heard this anecdote from Dr. Maskelyne 

Cc 



302 SIR ISAAC KEWTOX, 

and three female servants- In his own house he 
was hospitable and kind, and on proper occasions 
he gave splendid entertainments, though without 
ostentation or vanity. His own diet was frugal, and 
his dress was always simple ; but on one occasion, 
when he opposed the Honourable Mr. Annesley in 
1705, as a candidate for the university, he is said to 
have put on a suit of laced clothes. 

His generosity and charity had no bounds, and he 
used to remark, that they who gave away nothing 
till they died never gave at all. Though his wealth 
had become considerable by a prudent economy, yet 
he had always a contempt for money, and he spent 
a considerable part of his income in relieving the 
poor, in assisting his relations, and in encouraging 
ingenuity and learning. The sums which he gave 
to his relations at different times were enormous ;* 
and in 1724 he wrote a letter to the Lord Provost 
of Edinburgh, offering to contribute 20/. per annum 
to a provision for Mr. Maclaurin, provided he ac- 
cepted the situation of assistant to Mr. James Greg- 
ory, who was professor of mathematics in the uni- 
versity. 

The habits of deep meditation which Sir Isaac 
Newton had acquired, though they did not show 
themselves in his intercourse with society, exer- 
cised their full influence over his mind when in the 
midst of his own family. Absorbed in thought he 
would often sit down on his bedside after he rose, 
and remain there for hours without dressing himself, 
occupied with some interesting investigation which 
had fixed his attention. Owing to the same absence 
of mind, he neglected to take the requisite quantity 

* " He was very kind to all the Ayscoughs. To one h gave 8007., U 
another 2001, and to a third 100/., and many other sums ; and other en 
gagemems did he enter into also for them. He was the ready assistant 
of all who were any way related to him, to their children and grandchil- 
dren." Annual Register, 1776, vol. xix. p. 25. Sir Isaac gave some do* 
nations to the chapel and parish of Colstenvorth. Hearne says " that 
he promised to become a benefactor to the Royal Society, but failed " 



PERSONAL APPEARANCE. 303* 

oi nourishment, and it was therefore often necessary 
to remind him of his meals.* 

Sir Isaac Newton is supposed to have had little 
knowledge of the world, and to have been very ig- 
norant of the habits of society. This opinion has, 
we think, been rashly deduced from a letter which 
he wrote in the twenty-seventh year of his age to 
his young friend, Francis Aston, Esq., who was about 
to set out on his travels. This letter is a highly 
interesting production ; and while it shows much 
knowledge of the human heart, it throws a strong 
light upon the character and opinions of its author. 

In his personal appearance, Sir Isaac Newton was 
not above the middle size, and in the latter part of 
his life was inclined to be corpulent. According to 
Mr. Conduit " he had a very lively and piercing eye, 
a comely and gracious aspect, with a fine head of 
hair as white as silver, without any baldness, and 
when his peruke was off was a venerable sight." 
Bishop Atterbury asserts,! on the other hand, that 
the lively and piercing eye did not belong to Sir 
Isaac during the last twenty years of his life. " In- 
deed," says he, " in the whole air of his face and 
make there was nothing of that penetrating sagacity 
which appears in his compositions. He had some- 
thing rather languid in his look and manner which 
did not raise any great expectation in those who did 
not know him." This opinion of Bishop Atterbury 
is confirmed by an observation of Mr. Thomas 

* The following anecdote of Sir Isaac's absence has been published, 
but I cannot vouch for its authenticity. His intimate friend Dr. Stukely, 
who had been deputy to Dr. Hailey as secretary to the Royal Society, 
was one day shown into Sir Isaac's dining-room, where his dinner had 
been for some time served up. Dr. Stukely waited for a considerable 
*ime, and getting impatient, he removed the cover from a chicken, which 
he ate, replacing the bones under the cover. In a short time Sir Isaac 
entered the room, and after the usual compliments sat down to his din- 
ner, but on taking off tne cover, and seeing nothing but bones, he re- 
marked, " How absent we philosophers are. I really thought that 1 I) p 4 
BOt dined." 

t Epistolary Correspondence, vol. i. p. 180, sec. 71 



304 SIR ISAAC NEWTON. 

<r 

Hearne,* who says " that Sir Isaac was a man of no 
very promising aspect. He was a short, well-set 
man. He was full of thought, and spoke very little in 
company, so that his conversation was not agreeable. 
When he rode in his coach, one arm would be out 
of his coach on one side and the other on the other." 
Sir Isaac never wore spectacles, and never " lost 
more than one tooth to the day of his death." 

Besides the statue of S\r Isaac Newton executed 
by Roubiliac, there is a bust of him by the same 
artist in the library of Trinity College, Cambridge. 
Several good paintings of him are extant. Two 
of these are in the hall of the Royal Society of 
London, and have, we believe, been often engraved. 
Another, by Vanderbank, is in the apartments of 
the Master's lodge in Trinity College, and has been 
engraved by Vertue. Another, by Valentine Ritts, 
is in the landing-place near the entrance to Trinity 
College library ; but the best, from which our en- 
graving is copied, was painted by Sir Godfrey Knel- 
ler, and is in the possession of Lord Egremont at 
Petworth. In the university library there is pre- 
served a cast taken from his face after death. 

Every memorial of so great a man as Sir Isaac 
Newton has been preserved and cherished with pecu- 
liar veneration. His house at Woolsthorpe, of which 
we have given an engraving, has been. religiously 
protected by Mr. Tumor of Stoke Rocheford, the 
proprietor. Dr. Stukeley, who visited it in Sir 
Isaac's lifetime, on the 13th October, 1721, gives the 
following description of it in his letter to Dr. Mead, 
written in 1727 : " 'Tis built of stone as is the way 
of the country hereabouts, and a reasonable good 
one. They led me up stairs and showed me Sir 
Isaac's study, where I suppose he studied when in 
the country in his younger days, or perhaps when 
he visited his mother from the university. I ob- 
served the shelves were of his own making, being 
pieces of deal boxes which probably he sent his 
* MS. Memoranda in the Bodleian Library. 



MEMORIALS AND RECOLLECTIONS. 305 

books and clothes down in on those occasions. 

There were some years ago two or three hundred 
j books in it of his father-in-law, Mr. Smith, which 

Sir Isaac gave to Dr. Newton of our town."* 

When the house was repaired in 1798, a tablet of 
i white marble was put up by Mr. Turnor in the room 
[where Sir Isaac was born, with the following in- 
I scription : 

" Sir Isaac Newton, son of John Newton, Lord 
I of the manor of Woolsthorpe, was born in this room 

on the 25th December, 1642." 

Nature and Nature's laws lay hid in nign*, 
God said, '* Let Newton be," and all was light. 

The following lines have been written upon the 
house : 

Here Newton dawned, here lofty wisdom woke, 

And to a wondering world divinely spoke. 

If Tully glowed, when Phaedrus' steps he trode, 

Or fancy formed Philosophy a god ; 

If sages still for Homer's birth contend 

The Sons of Science at this dome must bend. 

All hail the shrine ! All hail the natal day, 

Cam boasts his noon, This Cot his morning ray. 

The house is now occupied by a person of the 
name of John Wollerton. It still contains the two 
dials made by Newton, but the styles of both are 
wanting. The celebrated apple-tree, the fall of one 
of the apples of which is said to have turned the 
attention of Newton to the subject of gravity, was 
destroyed by wind about four years ago ; but Mr. 
Turnor has preserved it in the form of a chair, f 

The chambers which Sir Isaac inhabited at Cam- 
bridge are known by tradition. They are the apart- 
ments next to the great gate of Trinity College, and 
it is believed that they then communicated by a 
staircase with the observatory in the Great Tower, 

* Tumor's Collections, p. 176. 

t The anecdote of the falling apple is mentioned neither by Dr. StuVely 
or by Mr. Conduit, and as I have not been able to find any authority for 
it whatever, I did not feel myself at liberty to use it. 

Cc2 



306 SIR ISAAC NEWTON, 

an observatory which was furnished by the contri 
butions of Newton, Cotes, and others. His telescope, 
represented in fig. 1, page 41, is preserved in the 
library of the Royal Society of London, and his globe, 
his universal ring-dial, quadrant, compass, and a re- 
flecting telescope said to have belonged to him, in 
the library of Trinity College. There is also in the 
same collection a long and curled lock of his sih er 
white hair. The door of his bookcase is in the Mu- 
seum of the Royal Society of Edinburgh. 

The manuscripts, letters, and other papers of New- 
ton have been preserved in different collections. His 
correspondence with Cotes relative to the second 
edition of the Principia, and amounting to between 
sixty and a hundred letters, a considerable portion 
of the manuscript of that work, and two or three 
letters to Dr. Keill on the Leibnitzian controversy, 
are preserved in the library of Trinity College, Cam- 
bridge. Newton's letters to Flamstead, about thirty- 
four in number, are deposited in the library of Corpus 
Christi College, Oxford.* Several letters of New- 
ton, and, we believe, the original specimen which he 
drew up of the Principia, exist among the papers of 
Mr. William Jones (the father of Sir William Jones), 
which are preserved at Shirburn Castle, in the library 
of Lord Macclesfield. But the great mass of New- 
ton's papers came into the possession of the Ports- 
mouth family through his niece, Lady Lymington, 
and have been safely preserved by that noble family. 
There is reason to believe that they contain nothing 
which could be peculiarly interesting to science ; but 
as the correspondence of Newton with contempo- 
rary philosophers must throw considerable light on 
his personal history, we trust that it will ere long be 
given to the public. 

* In the Monthly Review for August, 1829, p. 593, it is stated, that the 
correspondence between Newton and Flamstead, from 1680 to 1698, exists 
in the Sloane collection of Manuscripts in the British Museum. Pro- 
fessor Rigaud, however, has had the kindness to inquire into the accuracy 
of this statement, ana he has ascertained that these letters are merely 
copies, which., Dr. Birch had made from the originals at Oxford. 



(907) 



APPENDIX. 

No. I. 

OBSERVATIONS ON THE FAMILY OF SIR ISAAC NEWTON. * 

IN the year 1705, Sir Isaac gave into the Herald's 
Office an elaborate pedigree, stating upon oath that 
Tie had reason to believe that John Newton of Westby, 
n the county of Lincoln, was his great-grandfather's 
ather, and that this was the same John Newton who 
was buried in Basingthorpe church, on the 22d De- 
cember, 1563. This John Newton had four sons, 
'ohn, Thomas, Richard, and William Newton of 
runnerly, the last of whom was great-grandfather 
o Sir John Newton, Bart., of Hather. Sir Isaac 
considered himself as descended from the eldest of 
;hese, he having^ by tradition from his kindred ever 
since he can remember, reckoned himself next of kin 
among the Newtons) to Sir John Newton's family. 

The pedigree, founded upon these and other con- 
iderations, was accompanied by a certificate from 
Sir John Newton, of Thorpe, Bart., who states that 
hie had heard his father speak of Sir Isaac Newton 
s of his relation and kinsman, and that he himself 
elieved that Sir Isaac was descended from John New- 
on, son to John Newton of Westby, but knoweth not in 
mat particular manner. 

The pedigree of Sir Isaac, as entered at the Her- 
Id's Office, does not seem to have been satisfactory 
ither to himself or to his successors, as it could not 



308 APPENDIX. 

be traced with certainty beyond his grandfather ; and 
it will be seen from the following'interesting corres- 
pondence, that upon making further researches, he 
had found some reason to believe that he was of 
Scotch extraction. 

"Extract of a Letter from the Reverend Dr. Reid of 
Glasgow to Dr. Gregory of Edinburgh, dated 14^7 
March, 1784. 

" I send you on the other page an anecdote re 
specting Sir Isaac Newton, which I do not remem- 
ber whether I ever happened to mention to you in 
conversation. If his descent be not clearly ascer- 
tained (as I think it is not in the books I have seen), 
might it not be worth while to inquire if evidence 
can be found to confirm the account which he is said 
to have given of himself. Sheriff Cross was very 
zealous about it when death put a stop to his in- 
quiries. 

! "When I lived in old Aberdeen above twenty 
years ago, I happened to be conversing over a pipe 
of tobacco with a gentleman of that country, who 
had been lately at Edinburgh. He told me that he 
had been often in company with Mr. Hepburn of 
Keith, with whom I had the honour of some ac- 
quaintance. He said that, speaking of Sir Isaac 
Newton, Mr. Hepburn mentioned an anecdote, which 
he had from Mr. James Gregory, professor of mathe- 
matics at Edinburgh, which was to this purpose : 

" Mr. Gregory, being at London for some time 
after he resigned the mathematical chair, was often 
with Sir Isaac Newton. One day Sir Isaac said to 
him, ' Gregory, I believe you don't know that I am 
connected with Scotland-' ' Pray how, Sir Isaac V 
said Gregory. Sir Isaac said he was told that his 
grandfather was a gentleman of East Lothian ; that 
he came to London with King James si his acces- 
sion to the crown of England, and there spent his 



APPENDIX. 309 

brtune, as many more did at that time, by which his 
jon (Sir Isaac's father) was reduced to mean cir- 
cumstances. To this Gregory bluntly replied, 
Newton a gentleman of East Lothian, I never 
leard of a gentleman of East Lothian of that name.' 
Jpon this Sir Isaac said, ' that being very young 

en his father died, he had it only by tradition, 
ind it might be a mistake ;' and immediately turned 
;he conversation to another subject. 

" I confess I suspected that the gentleman who 
was my author had given some colouring to this 
story, and therefore I never mentioned it for a good 
nany years. 

" After I removed to Glasgow, I came to be very 
intimately acquainted with Mr. Cross, then sheriff 
)f Lanark, and one day at his own house mentioned 
;his story, without naming my author, of whom I 
expressed some diffidence. 

" The sheriff immediately took it up as a matter 
worth being inquired into. He said he was well 
acquainted with Mr. Hepburn of Keith (who was 
;hen alive), and that he would write him to know 
whether he ever heard Mr. Gregory say that he had 
such a conversation with Sir Isaac Newton. He 
said he knew that Mr. Keith, the ambassador, was 
also intimate with Mr. Gregory, and that he would 
write him to the same purpose. 

" Some time after, Mr. Cross told me that he had 
answers from both the gentlemen above mentioned, 
and that both remembered to have heard Mr. Greg- 
ory mention the conversation between him and Sir 
Isaac Newton, to the purpose above narrated, and 
at the same time acknowledged that they had made 
no further inquiry about the matter. 

" Mr. Cross, however, continued the inquiry, and 
a short time before his death told me that all he 
had learned was, that there is, or was lately, a baro- 
net's family of the name of Newton in West Lothian 
Mid Lothian (I have forgot which) : that there is 



310 APPENDIX. 

a tradition in that family that Sir Isaac Newto 
wrote a letter to the old knight that then was ( 
think Sir John Newton of Newton was his name] 
desiring to know what children, and particular!; 
what sons he had, their age, and what profession 
they intended : that the old baronet never deigne 
to return an answer to this letter, which his famil 
was sorry for, as they thought Sir Isaac might hav 
intended to do something for them." 

Several years after this letter was written, a Mi* 
Barren, a relation of Sir Isaac Newton, seems t 
have been making inquiries respecting the famil; 
of his ancestor, and in consequence of this the lat 
Professor Robison applied to Dr. Reid, to obtai 
from him a more particular account of the remark 
able conversation between Sir Isaac and Mr. Jame 
Gregory referred to in the preceding letter. I: 
answer to this request, Dr. Reid wrote the followin 
letter, for which I was indebted to John Robisor 
Esq. Sec. R. S. E., who found it among Ms father' 
manuscripts. 

Letter from Dr. Reid to Professor Robison respecting 
the Family of Sir Isaac Newton. 

" DEAR SIR, 

" I am very glad to learn by yours of April 4, tha 
a Mr. Barron, a near relation of Sir Isaac Newton 
is anxious to inquire into the descent of that grea 
man, as the family cannot trace it farther, with an; 
certainty, than his grandfather. I therefore, as yoi 
desire, send you a precise account of all I know 
and am glad to have this opportunity, before I die 
of putting this information in hands that will mak 
the proper use of it, if it shall be found of any use 

" Several years before I left Aberdeen (which 
did in 1764), Mr. Douglas of Feckel, the father o 
Sylvester Douglas, now a barrister at London, tol 



APPENDIX. 311 

ne, that having been lately at Edinburgh, he was 
)ften in company with Mr. Hepburn of Keith, a 
gentleman of whom I had some acquaintance, by 
lis lodging a night at my house at New Machar, 
vhen he was in the rebel army in 1745. That Mr. 
lepburn told him that he had heard Mr. James 
jiregory, professor of mathematics, Edinburgh, say, 
hat being one day in familiar conversation with 
Sir Isaac Newton at London, Sir Isaac said, ' Greg- 
ory, I believe you don't know that I am a Scotch- 
nan.' ' Pray," how is that ]' said Gregory. Sir 
saac said he was informed that his grandfather (or 
freat-grand father) was a gentleman of East (or 
Yest) Lothian : that he went to London with King 
ames the I. at his accession to the crown of Eng- 
and : and that he attended the court in expectation, 
s many others did, until he spent his fortune, by 
vhich means his family was reduced to low circum- 
tances. At the time this was told me Mr. Gregory 
vas dead, otherwise I should have had his own tes- 
imony, for he was my mother's brother. I likewise 
bought at that time that it had been certainly known 
tiat Sir Isaac had been descended from an old English 
amily, as I think is said in his eloge before the 
Academy of Sciences at Paris, and therefore I never 
nentioned what I had heard for many years, be- 
teving that there must be some mistake in it. 

" Some years after I came to Glasgow, I men- 
ioned (I believe for the first time) what I had heard 
o have been said by Mr. Hepburn to Mr. Cross, late 
heriff of this county, whom you will remember. 
Ir. Cross was moved by this account, and imme- 
iately said, 1 1 know Mr. Hepburn very well, and I 
.now he was intimate with Mr. Gregory : I shall 
vrite him this same night, to know whether he 
leard Mr. Gregory say so or not.' After some re- 
lection, he added, * I know that Mr. Keith, the am- 
assador, was also an intimate acquaintance of Mr. 
Gregory, and as he is at present in Edinburgh, I 
hall likewise write to him this night.* 



812 APPENDIX. 

" The next time I waited on Mr. Cross he told 
me that he had wrote both to Mr. Hepburn and Mr* 
Keith, and had an answer from both, and that both of 
them testified that they had several times heard Mr<s 
James Gregory say, that Sir Isaac Newton told him; 
what is above expressed, but that neither they noc 
Mr. Gregory, as far as they knew, ever made any* 
further inquiry into the matter. This appeared very 
strange both to Mr. Cross and me, and he said -hat 
would reproach them for their indifference, and 
would make inquiry as soon as he was able. 

" He lived but a short time after this, and in the 
last conversation I had with him upon the subject^ 
he said, that all he had yet learned was, that there 
was a Sir John Newton of Newton in one of the 
counties of Lothian (but I have forgot which), somd 
of whose chLdren were yet alive : that they reported 
that their father, Sir John, had a letter from Sir 
Isaac Newton, desiring to know the state of hia 
family, what children he had, particularly what sons^ 
and in what way they were. The old knight neve? 
returned an answer to this letter, thinking probably 
that Sir Isaac was some upstart, who wanted to 
claim a relation to his worshipful house. This omis* 
sion the children regretted, conceiving that Sir Isaac 
might have had a view of doing something for their 
benefit. 

" After this I mentioned occasionally in conver- 
sation what I knew, hoping that these facts might 
lead to some more certain discovery, but I found 
more coldness about the matter than I thought it 
deserved. I wrote an account of it to Dr. Gregory, 
your colleague, that he might impart it to any mem- 
ber of the Antiquarian Society who he judged 
might have the curiosity to trace the matter further. 

"In the year 1787, my colleague, Mr. Patrick 
Wilson, professor of astronomy, having been in j 
London, told me on his return that he had met ac- 
cidentally with a James Hutton, Esq. of Pimlico, 



APPENDIX. 313 

Westminster, a near relation of Sir Isaac Newton,* 
to whom he mentioned what he had heard from me 
with respect to Sir Isaac's descent, and that I wished 
much to know something more decisive on that sub- 
ject. Mr. Hutton said, if I pleased to write to him 
he would give me all the information he could give. 
I wrote him accordingly, and had a very polite 
answer, dated at Bath, 25th December, 1787, which is 
now before me. He says, ' I shall be glad when I 
return to London, if I can find in some old notes of 
my mother any thing that may fix the certainty of 
Sir Isaac's descent. If he spoke so to Mr. James 
Gregory, it is most certain he spoke truth. But Sir 
Isaac's grandfather, not his great-grandfather, must 
be the person who came from Scotland with King 
James I. If I find any thing to the purpose, I will 
take care it shall reach you.' 

" In consequence of this letter I expected another 
from Mr. Hutton when he should return to London, 
but have never had any. Mr. Wilson told me he 
was a very old man, and whether he be dead or alive 
I know not. 

" This is all I know of the matter, and for the 
facts above mentioned I pledge my veracity. I 
am much obliged to you, dear sir, for the kind ex- 
pressions of your affection and esteem, which, I 
assure you, are mutual on my part, and I sincerely 
sympathize with you on your afflicting state of 
health, which makes you consider yourself as out 
of the world, and despair of seeing me any more. 

" I have been long out of the world by deafness 
and extreme old age. I hope, however, if we should 
not meet again in this world, that we shall meet and 
renew our acquaintance in another. In the mean 
time, I am with great esteem, dear sir, yours affec- 
tionately, " THO. REID. 

" Glasgow College, 
" 
See page 288, note. 

Dd 



314 APPENDIX. 

This curious letter I published in the Ed. Phil. 
Journal for October 1, 1820. It excited the particular 
attention of the late George Chalmers, Esq., who 
sent me an elaborate letter upon the subject ; but as 
I was at that time in the expectation of obtaining 
some important information through other channels, 
this letter was not published. This hope, however, 
has been disappointed. A careful search has been 
made through the charter-chest of the Newtons 
of Newton in East Lothian, by Mr. Richard Play 
Newton, the representative of that family, but no 
document whatever has been found that can throw 
the least light upon the matter. It deserves to be 
remarked, however, that Sir Richard Newton, the 
alleged correspondent of Sir Isaac, appears to have 
destroyed his correspondence ; for though the char- 
ter-chest contains the letters of his predecessors for 
some generations, yet there is not a single epistolary 
document either of his own or of his lady's. 

Hitherto the evidence of Sir Isaac's Scottish de- 
scent has been derived chiefly from his conversation 
with Mr. James Gregory ; but I am enabled, by the 
kindness of Mr. Robison, to corroborate this evi- 
dence by the following information, derived, as will 
be .seen, from the family of the Newtons of Newton. 
Among various memoranda in the handwriting of 
Professor Robison, who at one time proposed to 
write the life of Sir Isaac, are the following : 

" 1st, Lord Henderland informed me in a letter 
dated March, 1794, that he had heard from his infancy 
that Sir Isaac considered himself as descended from 
the family of Newton of Newton. This he heard 
from his uncle Richard Newton of Newton (who 
was third son of Lord William Hay of Newhall) :" 
" He said that Sir Isaac wrote to Scotland to learn 
whether any descendants of that family remained, 
and this (it was thought) with the view to leave 
some of his fortune to the family possessing the 
estate with the title of baronet. Mr. Newton, not 



APPENDIX* 315 

laving this honour, and being a shy man, did not 
encourage the correspondence, because he did not 
considei himself as of kin to Sir Isaac, &c." 

" 2d, Information communicated to me by Hay 
Newton, Esq., of that ilk, 18th August, 1800." 

The late Sir Richard Newton of Newton, Bart, 
chief of that name, having no male children, settled 
;he estate and barony of Newton in East Lothian 
county upon his relation Richard Hay Newton, Esq., 
son of Lord William Hay."* " It cannot be dis- 
covered how long the family of Newton have been 
n possession of the barony, there being no tradition 
concerning that circumstance further than that they 
came originally from England at a very distant 
)eriod, and settled on these lands." " The celebrated 
Sir Isaac Newton was a distant relation of the 
family, and corresponded with the last baronet, the 
above-mentioned Sir Richard Newton." 

The preceding documents furnish the most com- 
pete evidence that the conversation respecting Sir 
'saac Newton's family took place between him and 
Mr. Gregory; and the testimony of Lord Henderland 
>roves that his own uncle, Richard Newton of New- 
on, the immediate successor of Sir Richard Newton, 
with whom Sir Isaac corresponded, was perfectly 
confident that such a correspondence took place. 

All these circumstances prove that Sir Isaac New- 
ton could not trace his pedigree with any certainty 
beyond his grandfather, and that there were two dif- 
ferent traditions in his family, one which referred 
his descent to John Newton of Westby, and the 
other to a gentleman of East Lothian who accom- 
panied King James VI. to England. In the first of 
these traditions he seems to have placed most confi- 
dence in 1705, when he drew out his traditionary 
pedigree ; but as the conversation w ith Professor 
James Gregory respecting his Scotch extraction 

* This entail was executed in 1724. a year or two before Sir Richard's 
. D. B. 



316 APPENDIX. 

tooK place twenty years afterward, namely, between 
1725 and 1727, it is probable that he had discovered 
the incorrectness of his first opinions, or at least 
was disposed to attach more importance to the other 
tradition respecting his descent from a Scotch family. 
In the letter addressed to me by the learned George 
Chalmers, Esq. I find the following observations 
respecting the immediate relations of Sir Isaac. 
" The Newtons of Woolsthorpe," says he, " who 
were merely yeomen farmers, were not by any 
means opulent. The son of Sir Isaac's father's 
brother was a carpenter called John. He was after- 
ward appointed gamekeeper to Sir Isaac, as lord 
of the manor, and died at the age of sixty in 1725. 
This John had a son, Robert, (John?) who was 
Sir Isaac's second cousin, and who became possessed 
of the whole land estates at and near Woolsthorpe, 
which belonged to the great Newton, as his heir-at- 
law.* Robert (John 1) became a worthless and disso- 
lute pers'on, who very soon wasted this ancient patri- 
mony, and falling down with a tobacco-pipe in his 
mouth when he was drunk, it broke in his throat, 
and put an end to his life at the age of thirty years, 
in 1737." 

No. II. 

LETTER FROM SIR ISAAC NEWTON TO FRANCIS ASTON, 
ESQ., A YOUNG FRIEND WHO WAS ON THE EVE OF SET- 
TING OUT UPON HIS TRAVELS. 

MR. ASTON was elected a Fellow of the Royal 
Society in 1678. He held the office of Secretary 
between 1681 and 1685 ; and he was the author of 
some observations on certain unknown ancient char- 
acters, which were published in the Philosophical 
Transactions for 1693. 

* See p. 291. 



APPENDIX. 317 

This letter has been referred to in pages 270 and 
303, and was written when Newton was only twen- 
ty-six years of age. It is in every respect an inter- 
esting document. 

" Trinity College^Canibridge^ 
" SIR, May 18, 1669. 

" Since in your letter you give mee so much 
liberty of spending my judgement about what may 
be to your advantage in travelling, I shall do it 
more freely than perhaps otherwise would have 
been decent. First, then, I will lay down some 
general rules, most of which, I believe, you have 
considered already ; but if any of them be new to 
you, they may excuse the rest ; if none at all, yet 
is my punishment more in writing than yours in 
reading. 

" When you come into any fresh company, 1. 
Observe their humours. 2. Suit your own carriage 
thereto, by which insinuation you will make their 
converse more free and open.' 3. Let your dis- 
corrs be more in querys and doubtings than peremp- 
tory assertions or disputings, it being the designe 
of travellers to learne, not to teach. Besides, it will 
persuade your acquaintance that you have the greater 
esteem of them, and soe make them more ready 
to communicate what they know to you ; whereas 
nothing sooner occasions disrespect and quarrels 
than peremtorinesse. You will find little or no 
advantage in seeming wiser or much more ignorant 
than your company. 4. Seldom discommend any 
thing though never so bad, or doe it but moderately, 
lest you bee unexpectedly forced to an unhansom 
retraction. It is safer to commend any thing more 
than it deserves, than to discommend a thing soe 
much as it deserves ; for commendations meet no" 
soe often with oppositions, or, at least, are no*" 
usually soe ill resented by men that think otherwise, 
as discommendations ; and you will insinuate into 



318 APPENDIX. 

men's favour by nothing sooner than seeming' to 
approve and commend what they like ; but beware 
of doing it by a comparison. 5. If you bee affronted, 
it is better, in a forraine country, to pass it by in 
silence, and with a jest, though with some dishonour, 
than to endeavour revenge ; for, in the first case, 
your credit's ne'er the worse when you return into 
England, or come into other company that have not 
heard of the quarrell. But, in the second case, you 
may beare the marks of the quarrell while you live, 
if you outlive it at all. But, if you find yourself un- 
avoidably engaged, 'tis best, I think, if you can com- 
mand your passion and language, to keep them 
pretty evenly at some certain moderate pitch, not 
much hightning them to exasperate your adversary, 
or provoke his friends, nor letting them grow over- 
much dejected to make him insult. In a word, if 
you can keep reason above passion, that and watch- 
fullnesse will be your best defendants. To which 
purpose you may consider, that, though such excuses 
as this, He provok't mee so much I could not for- 
bear, may pass among friends, yet amongst stran- 
gers they are insignificant, and only argue a travel- 
ler's weaknesse. 

" To these I may add some general heads for in- 
quirys or observations, such as at present I can 
think on. As, 1. To observe the policy s, wealth, 
and state-affairs of nations, so far as a solitary 
traveller may conveniently doe. 2. Their imposi- 
tions upon all sorts of people, trades, or commoditys, 
that are remarkable. 3. Their laws and customs, 
how far they differ from ours. 4. Their trades and 
arts wherein they excell or come short of us in 
England. 5. Such fortifications as you shall meet 
with, their fashion, strength, and advantages for de- 
fence, and other such military affairs as are consider- 
able. 6. The power and respect belonging to their 
degrees of nobility or magistracy. 7. It will not be 
time mispent to make a catalogue of the names and 



APPENDIX. 319 

excellencys of those men that are most wise, learned, 
or esteemed in any nation. 8. Observe the mecha- 
nisme and manner of guiding ships. 9. Observe the 
products oi nature in several places, especially in 
mines, with the circumstances of mining arid of ex- 
tracting metals or minerals out of their oare, and of 
refining them ; and if you meet with any transmuta- 
tions out of their own species into another (as out 
of iron into copper, out of any metall into quicksilver, 
out of one salt into another, or into an insipid body, 
&c.), those, above all, will be worth your noting, 
being the most luciferous, and many times lucrife- 
rous experiments too, in philosophy. 10. The prices 
of diet and other things. 11. And the staple com- 
moditys of places. 

"These generals (such as at present I could 
think of), if they will serve for nothing else, yet they 
may assist you in drawing up a modell to regulate 
your travells by. As for particulars, these that fol- 
low are all that I can now think of, viz. Whether 
at Schemnitium, in Hungary (where there are mines 
of gold, copper, iron, vitrioll, antimony, &c.), they 
change iron into copper by dissolving it in a vitriolate 
water, which they find in cavity s of rocks in the 
mines, and then melting the slimy solution in a 
strong fire, which in the cooling proves copper. The 
like is said to be done in other places, which I can- 
not now remember ; perhaps, too, it may be done in 
Italy. For about twenty or thirty years agone there 
was a certain vitrioll came from thence (called 
Roman vitrioll), but of a nobler virtue than that 
which is now called by that name ; which vitrioll is 
not now to be gotten, because, perhaps, they make 
a greater gain by some such trick as turning iron into 
copper with it than by selling it. 2. Whether, in 
Hungary, Sclavonia, Bohemia, near the town Eila, 
or at the mountains of Bohemia near Silesia, there 
be rivers whose waters are impregnated with gold ; 
perhaps, the gold being dissolved by some corrosive 



320 APPENDIX. 

waters like aqua regis, and the solution carried 
along with the streame, that runs through the mines. 
And whether the practice of laying mercury in the 
rivers, till it be tinged with gold, and then straining 
the mercury through leather, that the gold may stay 
behind, be a secret yet, or openly practised. 3. 
There is newly contrived, in Holland, a mill to grind 
glasses plane withall, and I think polishing them 
too ; perhaps it will be worth the while to see it. 

4. There is in Holland one Borry, who some 

years since was imprisoned by the Pope, to have 
extorted from him secrets (as I am told) of great 
worth, both as to medicine and profit, but he escaped 
into Holland, where they have granted him a guard. 
J think he usually goes clothed in green. Pray in- 
quire what you can of him, and whether his ingenuity 
be any profit to the Dutch. You may inform your- 
self whether the Dutch have any tricks to keep their 
ships from being all worm-eaten in their voyages to 
the Indies. Whether pendulum clocks do any ser- 
vice in finding out the longitude, &c. 

" I am very weary, and shall not stay to part with 
a long compliment, only I wish you a good journey, 
and God be with you. 

"Is. NEWTON. 

" Pray let us hear from yon in your travells. 1 
have given your two books to Dr. Arrowsmith " 



No. III. 

A REMARKABLE AND CURIOUS CONVERSATION BETWEEN 
SIR ISAAC NEWTON AND MR. CONDUIT." 

" I WAS on Sunday night, the 7th of March, 1724-5, 
at Kensington with Sir Isa&v, Newton, in his lodgings, 
just after he was come out of a fit of the gout, 
which he had had in both his feet, for the first time, 



APPENDIX. 321 

in the eighty-third year of his age. He was better 
after it, and his head clearer, and memory stronger 
than I had known them for some time. He then 
repeated to me, by way of discourse, very distinctly, 
though rather in answer to my queries than in one 
continued narration, what he had often hinted to 
me before, viz. that it was his conjecture (he would 
affirm nothing) that there was a sort of revolution 
in the heavenly bodies ; that the vapours and light 
emitted by the sun, which had their sediment as 
water and other matter, had gathered themselves 
by degrees into a body, and attracted more matter 
from the planets, and at last made a secondary 
planet (viz. one of those that go round another 
planet and then by gathering to them, and attract- 
ing more matter, became a primary planet ; and 
then by increasing still became a comet, which after 
certain revolutions, by coming nearer and nearer to 
the sun, had all its volatile parts condensed, and 
became a matter fit to recruit and replenish the sun 
(which must waste by the constant heat and light 
it emitted) as a fagot would this fire if put into it 
I (we were sitting by a wood fire), and that that 
would probably be the effect of the comet of 1680, 
sooner or later, for, by the observations made upon 
it, it appeared, before it came near the sun, with 
a tail only two or three degrees long ; but by the 
heat it contracted in going so near the sun, it 
seemed to have a tail of thirty or forty degrees 
when it went from it ; that he could not say when 
this comet would drop into the sun ; it might perhaps 
have five or six revolutions more first, but whenever 
it did it would so much increase the heat of the sun 
that this earth would be burnt, and no animals in it 
could live. That he took the three phenomena seen 
by Hipparchus, Tycho Brahe, and Kepler's disciples 
to have been of this kind, for he could not otherwise 
account for an extraordinary light as those were, 
appearing all at once among the fixed stars (all 



322 APPENDIX. 

which he took to be suns enlightening other planets 
as our sun does ours) as big as Mercury or Venus 
seems to us, and gradually diminishing for sixteen 
months, and then sinking into nothing. He seemed 
to doubt whether there were not intelligent beings 
superior to us who superintended these revolutions 
of the heavenly bodies by the direction of the 
Supreme Being. He appeared also to be very 
clearly of opinion that the inhabitants of this world 
were of a short date, and alleged as one reason for 
that opinion, that all arts, as letters, ships, printing, 
needle, &c., were discovered within the memory of 
history, which could not have happened if the world 
had been eternal ; and that there were visible marks 
of ruin upon it which could not be effected by a 
flood only. When I asked him how this earth could 
have been repeopled if ever it had undergone the 
same fate it was threatened with hereafter by the 
comet of 1680, he answered, that required the power 
of a Creator. He said he took all the planets to be 
composed of the same matter with this earth, viz. 
earth, water, stones, &c., but variously concocted. 
I asked him why he would not publish his conjec- 
tures as conjectures, and instanced that Kepler had 
communicated his ; and though he had not gone 
near so far as Kepler, y^i Kepler's guesses were so 
just and happy that they uad been proved and 
demonstrated by him. His answer was, ' I do not 
deal in conjectures.' But upon my talking to him 
about the four observations that had been made of 
the comet of 1680, at 574 years' distance, and asking 
him the particular times, he opened his Principia, 
which laid on the table, and showed me there the 
particular periods, viz. 1st, the Julium Sidus, in the 
time of Justinian, in 1106, in 1680. 

And I, observing that he said there of that comet, 
'incidet in corpus solis,' and in the next paragraphs 
adds, ' stellae fixae refici possunt,' told him I thought 
he owned there what we had been talking about, 



APPENDIX. 323 

that the comet would drop into the sun, and that fixed 
stars were recruited and replenished by comets 
when they dropped into them ; and, consequently, 
that the sun would be recruited too ; and asked him 
why he would not own as freely what he thought of 
the sun as well as what he thought of the fixed stars. 
He said, * that concerned us more ;' and, laughing, 
added, 4 that he had said enough for people to know 
his meaning.' n 

The preceding paper, with the title prefixed to it, 
was first published by Mr. Turner in his Collections, 

c. p. 172. It was found among the Portsmouth 
aanuscripts, in the handwriting of Mr. Conduit. 



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